Infrared fluorescent coatings

ABSTRACT

The present invention provides for a composition comprising a pigment, wherein the composition is suitable for coating a surface that is, or is expected to be, exposed to the sun. The pigment comprises particles that fluoresce in sunlight, thereby remaining cooler in the sun than coatings pigmented with non-fluorescent particles. The particles comprise solids that fluoresce or glow in the visible or near infrared (NIR) spectra, or that fluoresce when doped. Suitable dopants include, but are not limited to, ions of rare earths and transition metals. A coating composition includes: (i) a film-forming resin; (ii) an infrared reflective pigment; and (iii) an infrared fluorescent pigment different from the infrared reflective pigment. When the coating composition is cured to form a coating and exposed to radiation comprising fluorescence-exciting radiation, the coating has a greater effective solar reflectance (ESR) compared to the same coating exposed to the radiation comprising fluorescence-exciting radiation except without the infrared fluorescent pigment. A multi-layer coating including the coating composition, and a substrate at least partially coated with the coating composition is also disclosed. A method of reducing temperature of an article includes applying the coating composition to at least a portion of the article.

STATEMENT OF GOVERNMENTAL SUPPORT

The invention was made with government support under Contract Nos.DE-AC02-05CH11231 and DE-EE-0006347 awarded by the U.S. Department ofEnergy. The government has certain rights in the invention.

FIELD OF THE INVENTION

The present invention is in the field of cool building materials. Thepresent invention also relates to a coating composition including a filmforming resin, an infrared reflective pigment, and an infraredfluorescent pigment different from the infrared reflective pigment. Thepresent invention also relates to a multi-layer coating composition, acoated substrate, and a method of reducing temperature of an article.

BACKGROUND OF THE INVENTION

Current work on cool materials (particularly for roofing) has focused onthe basic idea to find various colored materials, such as coatings,tiles, roofing granules, etc., that stay cooler in the sun thanconventional materials. White materials are usually best, but architectsand building owners often prefer non-white and even dark materials. Todate, this has been done by selecting pigments (colorants) that do notabsorb the near-infrared (“NIR”), i.e., radiation having a wavelength offrom 700 to 2500 nm, portion of sunlight. Reflection of the NIR can theneither be accomplished by the pigment itself or by a white (or otherNIR-reflecting) underlayer. Commercially available selective blacksinclude the mixed metal oxides such as x Fe₂O₃.(1−x) Cr₂O₃ (where xvaries) and a perylene organic black. These materials absorb lightacross visible spectrum (400 to 700 nm), and do not absorb light in thenear infrared (700 to about 2500 nm). Thus, these pigments can be usedto fabricate cool black materials. Grouping the mere 5% of the solarspectrum in the UV with the visible 45%, one can say that the solarspectrum is about one-half UV/VIS and about one-half in the NIR. Thevisible reflectance of black is usually about 0.05%. If the NIRreflectance can be very high, e.g. 0.95%, then the overall solarreflectance of a cool selective black can be up to, but not exceed,0.50%. In a similar manner, the reflectance of other specified darkcolors is limited because absorption in the visible is required toformulate a dark color.

For many coating applications in building materials, dark colors, suchas black, dark red, and dark blue are particularly desirable foraesthetic purposes. However, dark colored building materials, facades,and roofs are susceptible to absorption of infrared (“IR”) radiation.These dark structures reflect insignificant amounts of IR radiation.While IR radiation extends from the nominal red edge of the visiblespectrum at 700 nm to 1 mm, NIR radiation, constitutes about 45% of thesolar energy that reaches the earth's surface. As a result, thestructures exhibit increased temperatures and become quite hot,particularly on sunny days in warm and hot climates, rendering theiroccupants uncomfortable. In addition, such buildings are then moreexpensive to operate and require more energy, since higher levels of airconditioning are required to maintain a certain level of comfort ascompared to structures having lighter colors with higher reflectivity.Similarly, transportation vehicles such as aircrafts or automobiles cansuffer excessive solar heat gain when coated with dark colors andrequire more air conditioning to maintain comfortable climate control.In addition, objects made with composites, such as fiber reinforcedpolymer composites, can suffer mechanical damage from overheating due tosolar heat gain and often require lighter colors to maintain compositesurface temperatures below a critical operating maximum. Therefore,coating compositions that are able to provide cool coatings with reducedIR absorptance are desirable.

SUMMARY OF THE INVENTION

The present invention provides for a composition comprising fluorescentpigment, wherein the composition is suitable for coating a surface thatis, or is expected to be, exposed to the sun. The fluorescent pigmentcomprises particles that fluoresce in sunlight, thereby remaining coolerin the sun than coatings pigmented with non-fluorescent particles. Theparticles comprise solids that fluoresce in the visible or near infrared(NIR) spectra, or that fluoresce when doped. Suitable dopants include,but are not limited to, ions of rare earths and transition metals.

The present invention provides for a composition suitable for coating asurface that is, or is expected to be, exposed to the sun, comprising ametal oxide or fluoride, or metal compound, or a mixture thereof, thatfluoresces and/or has a near infrared (NIR) reflectance, such aswavelength(s) within the 700 to 1,500 nm range, or fluoresces or glowsin the near infrared or visible when excited by light, such as sunlight.

In some embodiments, the composition has a dark color. The metal oxideor fluoride, or metal compound, or a mixture thereof, is capable offluorescing in the visible and/or near-infrared. In some embodiments,when a surface is coated with the composition, the surface has aneffective solar reflectance (ESR) that is equal to or over 0.4, 0.5,0.6, or 0.7.

The present invention provides for the use of fluorescent pigments topermit various colored materials to remain cooler in the sun than theconventional, non-fluorescent pigments currently in use for thispurpose. One aspect of the invention is that the design of the coatings(and other materials) with specified color must be modified such thatabsorbed energy is not converted to heat, but re-radiated. In someembodiments, the conventional cool pigments are used sparingly.

The present invention also includes a coating composition including: (i)a film-forming resin; (ii) an infrared reflective pigment; and (iii) aninfrared fluorescent pigment different from the infrared reflectivepigment. When the coating composition is cured to form a coating andexposed to radiation comprising fluorescence-exciting radiation, thecoating has a greater effective solar reflectance (ESR) compared to thesame coating exposed to the radiation comprising fluorescence-excitingradiation except without the infrared fluorescent pigment.

The present invention is also directed to a multi-layer coatingincluding: (i) a first coating layer comprising a cured infraredreflective coating composition; and a second coating layer overlaying atleast a portion of the first coating layer. The second coating layerincludes a cured coating composition including: (i) a film-formingresin; (ii) an infrared reflective pigment; and (iii) an infraredfluorescent pigment different from the infrared reflective pigment, andwhen the coating composition is cured to form a coating and exposed toradiation comprising fluorescence-exciting radiation, the coating has agreater effective solar reflectance (ESR) compared to the same coatingexposed to the radiation comprising fluorescence-exciting radiationexcept without the infrared fluorescent pigment.

The present invention is also directed to a substrate at least partiallycoated with a coating composition including: (i) a film-forming resin;(ii) an infrared reflective pigment; and (iii) an infrared fluorescentpigment different from the infrared reflective pigment. When the coatingcomposition is cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, the coating has a greatereffective solar reflectance (ESR) compared to the same coating exposedto the radiation comprising fluorescence-exciting radiation exceptwithout the infrared fluorescent pigment.

The present invention is also directed to a method of reducing thetemperature of an article including: (a) applying a coating compositionto at least a portion of a surface of an article, the coatingcomposition comprising (i) a film-forming resin, (ii) an infraredreflective pigment, and (iii) an infrared fluorescent pigment differentfrom the infrared reflective pigment; and (b) curing the coatingcomposition to form a coating on the article. When the coatingcomposition is cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, the coating has a greatereffective solar reflectance (ESR) compared to the same coating exposedto the radiation comprising fluorescence-exciting radiation exceptwithout the infrared fluorescent pigment.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and others will be readily appreciated by theskilled artisan from the following description of illustrativeembodiments when read in conjunction with the accompanying drawings.

FIG. 1 is a graph showing the X-ray diffraction (XRD) patterns of Al₂O₃doped with 1 wt % Cr₂O₃ and 3 wt % of Cr₂O₃;

FIG. 2 shows micrographs of two different Al₂O₃:Cr pigments obtained byscanning electron microscopy (SEM);

FIG. 3 shows a plot of the surface temperatures versus time ofcalibration panels;

FIG. 4 shows a fluorescence spectra for 3 wt % Cr₂O₃ doped Al₂O₃pigments excited at 500 nm;

FIG. 5 shows a fluorescence spectra for Egyptian blue pigments excitedat 600 nm;

FIGS. 6A and 6B are graphs showing fluorescence spectra ofhighly-pigmented coatings with 500 g/m² of 0 to 3 wt % Cr₂O₃ doped Al₂O₃obtained with NIR spectrofluorometers;

FIG. 7 is a graph showing the fluorescence spectra for a) an Egyptianblue pigment, b) a 0.14 P:B Egyptian blue coating over chrome primedaluminum substrate and c) a 0.4 P:B Egyptian blue coating over a chromeprimed aluminum substrate;

FIG. 8 is a graph of NIR fluorescence spectra for a) Egyptian blue andb) Han purple coatings over a white substrate;

FIG. 9 is a graph showing reflectance of Cd pigments in acrylic-basedartists paints over a white substrate;

FIG. 10 shows a graph of reflectance of 3 cadmium pigments (dark red,medium red, and light red) and a zirconia red pigment;

FIG. 11 shows a graph of spectral reflectance of smalt blue (CoO.K.Si)as compared to the spectral reflectance of Egyptian blue (CaCuSi₄O₁₀);

FIG. 12 shows NIR fluorescence spectra of several alkali earth coppersilicates;

FIG. 13 shows plots of spectral reflectance for PVDF-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white and yellow substrates;

FIG. 14 shows plots of spectral reflectance for acrylic-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white substrates;

FIG. 15 shows reflectance of the yellow primer and the white-coatedsubstrates used as the underlayer for the coatings of FIGS. 13 and 14 ;

FIG. 16A shows fluorescence from several samples made with SrCuSi₄O₁₀(large particle size); FIG. 16B shows plots similar to those of FIG.16A, but utilizing the Ba(La,Li)CuSi₄O₁₀ (small particle size); FIG. 16Cshows reflectance data that corresponds to FIGS. 16A and 16B; FIG. 16Dshows fluorescence of a strontium compound doped with equal amounts ofLa and Li, compared with an undoped material; FIG. 16E shows reflectancedata corresponding to FIG. 16D; FIG. 16F shows fluorescence data on aBaCuSi₄O₁₀ sample that is contaminated with CuO; FIG. 16G showsreflectance data corresponding to the prior fluorescence plot; FIG. 16Hshows fluorescence of Egyptian blue samples; FIG. 16I shows reflectancedata corresponding to FIG. 16H;

FIG. 17 shows nine NIR fluorescence spectra corresponding to coatingscontaining 1.5 wt % Cr₂O₃ doped Al₂O₃ in PVDF-based coatings at threeP:B ratios (0.2, 0.4, and 0.8) and three film thicknesses (1 coat, 2coats, 3 coats) per P:B ratio;

FIG. 18 shows temperature measurements for 18 test samples and 4calibrated reference samples;

FIG. 19 shows NIR fluorescence spectra for PVDF-based coatingscontaining Sr(La,Li)CuSi₄O₁₀ at P:B ratios of 0.2, 0.4 and 0.8 appliedover aluminum substrates coated with a yellow chrome primer and whiteprimer with film thicknesses for each P:B coating of 0.8 mils, 1.6 milsand 2.4 mils;

FIG. 20 shows peak heights of the coatings of FIG. 19 as a function ofthe product of P:B ratio and coating thickness;

FIG. 21 shows A) substrates coated with dark brown PVDF-based coatingswith varying weight percentages of ruby pigment and B) substrates coatedwith black PVDF-based coatings with varying weight percentages of HanBlue pigment;

FIG. 22 shows coatings including Sr(La,Li)CuSi₄O₁₀ (Top),Sr(La,Li)CuSi₄O₁₀ with azo yellow (Bottom left) and Sr(La,Li)CuSi₄O₁₀with Shepherd yellow 193 (Bottom right);

FIG. 23 shows a photograph of a blue-shade black sample made with aSrCuSi₄O₁₀ (large) pigmented acrylic coating over orange over a brightwhite substrate;

FIG. 24 shows Left: a coating containing NIR fluorescent pigment (Hanblue pigment) and IR reflective pigment (Shepherd 10C341)—Right: acoating containing IR reflective pigment (Shepherd 10C341);

FIG. 25 shows NIR fluorescence spectra of a coating containing NIRfluorescent blue/IR reflective orange and a coating containing IRreflective pigments;

FIG. 26 shows a plot of thermal measurements conducted on severalcoatings containing varying levels of NIR fluorescent ruby pigment;

FIG. 27 shows a photo of the samples in sunlight, wherein on the left isthe off-white reference, and on the right is the experimental samplewhich includes a layer of synthetic rubies;

FIG. 28 shows a graph where pink dots show the temperature of the sampleunder test as it warms in the sun, wherein three calibratednon-fluorescent samples are labeled with their spectrometer-determinedsolar absorptance values, and temperature fluctuations are caused bylight gusts of wind; and

FIG. 29 shows SR verses concentration of Cr₂O₃, wherein the top curve isthe effective SR as determined by temperature measurements in the sun,the middle curve is the standard spectrometer-determined solarreflectance without regard to fluorescence (it would be identical to thetop curve if no fluorescence were present), and the bottom curve is thereflectance at 550 nm, which is a measure of visual brightness.

DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described, it is to be understood thatthis invention is not limited to particular embodiments described, assuch may, of course, vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only, and is not intended to be limiting, since the scope ofthe present invention will be limited only by the appended claims.

All patents, patent applications, and publications mentioned herein arehereby incorporated by reference in their entireties.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassedwithin the invention. The upper and lower limits of these smaller rangesmay independently be included or excluded in the range, and each rangewhere either, neither or both limits are included in the smaller rangesis also encompassed within the invention, subject to any specificallyexcluded limit in the stated range. Where the stated range includes oneor both of the limits, ranges excluding either or both of those includedlimits are also included in the invention.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although any methods andmaterials similar or equivalent to those described herein can be used inthe practice or testing of the present invention, the preferred methodsand materials are now described. All publications mentioned herein areincorporated herein by reference to disclose and describe the methodsand/or materials in connection with which the publications are cited.

The terms “optional” or “optionally” as used herein mean that thesubsequently described feature or structure may or may not be present,or that the subsequently described event or circumstance may or may notoccur, and that the description includes instances where a particularfeature or structure is present and instances where the feature orstructure is absent, or instances where the event or circumstance occursand instances where it does not.

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers expressing, for example, quantities ofingredients used in the specification and claims are to be understood asbeing modified in all instances by the term “about”. Accordingly, unlessindicated to the contrary, the numerical parameters set forth in thefollowing specification and attached claims are approximations that mayvary depending upon the desired properties to be obtained by the presentinvention. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

In this application, the use of the singular includes the plural andplural encompasses singular, unless specifically stated otherwise. Inaddition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances. Further, in this application, the use of “a”or “an” means “at least one” unless specifically stated otherwise. Forexample, “a” pigment, “a” film-forming resin, “an” inorganic oxide, andthe like refer to one or more of any of these items. Also, as usedherein, the term “polymer” is meant to refer to prepolymers, oligomersand both homopolymers and copolymers. The term “resin” is usedinterchangeably with “polymer.” The term “metal” includes metals, metaloxides, and metalloids.

As used herein “wavelength” includes a spectral range of wavelengths,such as a spectral peak having a 25 nm, 50 nm, 75 nm, 100 nm, 125 nm,200 nm range on both sides of the spectral peak. As such, “wavelength”may refer to a spectral range of wavelengths encompassing up to 50 nm,up to 100 nm, up to 150 nm, up to 200 nm, up to 250 nm, up to 400 nm.

These and other objects, advantages, and features of the invention willbecome apparent to those persons skilled in the art upon reading thedetails of the invention as more fully described below.

The present invention provides for a composition suitable for coating asurface that is, or is expected to be, exposed to the sun, comprising ametal oxide or fluoride, or a mixture thereof, that fluoresces and/orhas a near infrared (NIR) reflectance, such as wavelength(s) within the700 to 1,500 nm range, or fluoresces or glows in the near infrared orvisible when excited by light, such as sunlight. In some embodiments,the wavelength(s) are within the 700 to 1,000 nm range. In someembodiments, the composition has a dark color. The metal oxide orfluoride, or metal compound, or a mixture thereof, is capable offluorescing in the visible and/or near-infrared. In some embodiments,when a surface is coated with the composition, the surface has aneffective solar reflectance (ESR) that is equal to or over 0.4, 0.5,0.6, or 0.7.

In some embodiments, the composition includes an IR fluorescent pigmentwhich may be a metal oxide or fluoride, or metal compound, achieve anESR value that is equal to or over 0.4, 0.5, 0.6, or 0.7. In someembodiments, the composition or metal oxide or fluoride, or metalcompound, can achieve an ESR value that ranges from about equal to orover 0.4 to equal or lower than 0.7. In some embodiments, thecomposition or metal oxide or fluoride, or metal compound, can achievean ESR value that ranges from about equal to or over 0.5 to equal orlower than 0.7. In some embodiments, the composition or metal oxide orfluoride, or metal compound, can achieve an ESR value that ranges fromabout equal to or over 0.6 to equal or lower than 0.7.

In some embodiments, the composition is a liquid, a colloid, or asolution suitable for coating, or a coating composition for applicationto a substrate or a coating applied on a surface of a substrate that is,or is expected to be, exposed to the sun. In some embodiments, thecomposition is a solid.

The present invention is directed to a coating composition including afilm-forming resin, an infrared (“IW”) reflective pigment, and an IRfluorescent pigment different from the IR reflective pigment. When thecoating composition is cured to form a coating and exposed tofluorescence-exciting radiation, the coating has a greater effectivesolar reflectance (ESR) compared to the same coating exposed to thefluorescence-exciting radiation except without the IR fluorescentpigment.

IR Reflective Pigment

The coatings according to the present invention may include one or moreIR reflective pigments. As used herein, the term “IR reflective pigment”refers to a pigment that, when included in a curable coatingcomposition, provides a cured coating that reflects IR radiation, suchas NIR radiation, greater than a cured coating deposited in the samemanner from the same composition but without the IR reflective pigment.As used herein, IR radiation refers to radiation energy having awavelength ranging from 700 nanometers to 1 millimeter. NIR radiationrefers to radiation energy have a wavelength ranging from 700 to 2500nanometers. The IR reflective pigment may reflect environmental IRradiation as well as radiation produced by the IR fluorescent pigment ordye described below. The coating may comprise the IR reflective pigmentin an amount sufficient to provide a cured coating that has a solarreflectance, measured according to ASTM E903-96 in the wavelength rangeof 700-2500 nm, that is at least 2, or at least 5 percentage pointshigher than a cured coating deposited in the same manner from the samecoating composition in which the IR reflective pigment is not present.Non-limiting examples of IR reflective pigments include inorganic ororganic materials. Non-limiting examples of suitable IR reflectivepigments include any of a variety of metals and metal alloys, inorganicoxides, and interference pigments. Non-limiting examples of IRreflective pigments include titanium dioxide, titanium dioxide coatedmica flakes, iron titanium brown spinel, chromium oxide green, ironoxide red, chrome titanate yellow, nickel titanate yellow, blue andviolet. Suitable metals and metal alloys include aluminum, chromium,cobalt, iron, copper, manganese, nickel, silver, gold, iron, tin, zinc,bronze, brass, including alloys thereof, such as zinc-copper alloys,zinc-tin alloys, and zinc-aluminum alloys, among others. Some specificnon-limiting examples include nickel antimony titanium, nickel niobiumtitanium, chrome antimony titanium, chrome niobium, chrome tungstentitanium, chrome iron nickel, chromium iron oxide, chromium oxide,chrome titanate, manganese antimony titanium, manganese ferrite,chromium green-black, cobalt titanates, chromites, or phosphates, cobaltmagnesium and aluminites, iron oxide, iron cobalt ferrite, irontitanium, zinc ferrite, zinc iron chromite, copper chromite, as well ascombinations thereof.

More particularly, commercially available non-limiting examples of IRreflective pigments include RTZ Orange 10C341 (rutile tin zinc), Orange30C342, NTP Yellow 10C151 (niobium tin pyrochlore), Azo Yellow, Yellow10C112, Yellow 10C242, Yellow 10C272, Yellow 193 (chrome antimonytitanium), Yellow 30C119, Yellow 30C152, Yellow 30C236, Arctic Black10C909 (chromium green-black), Black 30C933, Black 30C941, Black 30C940,Black 30C965, Black 411 (chromium iron oxide), Black 430, Black 20C920,Black 444, Black 10C909A, Black 411A, Brown 300888, Brown 200819, Brown157, Brown 100873, Brown 12 (zinc iron chromite), Brown 8 (iron titaniumbrown spinel), Violet 11, Violet 92, Blue 300588, Blue 300591, Blue300527, Blue 385, Blue 424, Blue 211, Green 260, Green 223, Green 187B,Green 410, Green 300612, Green 3006054, Green 300678, and mixturesthereof. The IR reflective pigments can be added to the coatingcomposition in any suitable form, such as discrete particles,dispersions, solutions, and/or flakes.

The IR reflective pigments can also be incorporated into the coatingcomposition in any suitable form, e.g., by use of a grind vehicle, suchas an acrylic grind vehicle, the use of which will be familiar to oneskilled in the art. The IR reflective pigments, if they do not absorbthe IR fluorescence emission, can be used to adjust the visible color ofthe coating composition.

IR Fluorescent Pigment

As previously mentioned, the coating composition of the presentinvention includes at least one IR fluorescent pigment. As used herein,the term “IR fluorescent pigment” refers to a pigment which fluorescesin the IR region (700 nm-1 mm) of the electromagnetic spectrum. The IRfluorescent pigment may fluoresce in the NIR region (700-2500 nm) of theelectromagnetic spectrum. The IR fluorescent pigment may fluoresce at alower energy wavelength when excited by a higher energy wavelength. Forinstance, the IR fluorescent pigment may fluoresce in the 700-1500 nmregion (a comparatively lower energy wavelength) when excited byradiation in the 300-700 nm region (a comparatively higher energywavelength).

Phosphors with a Transparent Matrix (Wide Band Gap Materials)

In some embodiments, the IR fluorescent pigment comprises a transparenthost material that is glassy, crystalline, polycrystalline, ornanocrystalline. If the host materials is visibly transparent, its bandgap must be larger than 3.1 eV, so that intrinsic absorption occurs onlyat non-visible (e.g., UV) wavelengths. This material requires additionof dopant ions (and/or impurities, defects, etc.) so that it can absorbmore sunlight than the minor 5% ultraviolet component, and may alsorequire dopants so that the fluorescent emission is in the spectralrange of interest.

Many phosphors for fluorescent lamps are known. They require strong UVabsorption and, generally, strong visible emission. Recipes forsynthesizing about 200 of these materials may be found in (Inorganicphosphors [electronic resource]: compositions, preparation and opticalproperties, William M Yen and Marvin J. Weber, eds., Willi Lehmann,additional author, Boca Raton: CRC Press (2004)). Modification of theserecipes can be performed by substitution of atoms by chemically similaratoms that are lower down in the periodic table. If the substitutions donot lead to different crystal structures, the corresponding band gapsare usually smaller, leading to more absorption in the 400 to 600 nmrange. Also, visibly emitting dopants can be replaced by those withthose emitting in the near infrared. For example, Eu³⁺ used as a redemitter (about 600 nm) can be replaced with Cr³⁺, emitting in the 695 to800 nm range.

Semiconductor Phosphors

In some embodiments, the IR fluorescent pigment comprises semiconductorswhich have a direct band gap and are particularly useful for absorbingand emitting radiant energy. (The term direct gap means that the maximumin the valence band and the minimum in the conduction band reside at thesame position in momentum space.) With a direct gap radiativerecombination of electrons and holes can occur with a high probabilityas no phonons are necessary to provide conservation of momentum.Materials that are pure and defect free can efficiently emit light withphoton energy equal to the band gap (plus the kinetic energy of anelectron and hole, a few tens of electron millivolts). Thus, in somecases, semiconductor phosphors require no dopants. Materials that aredoped or have native defects (e.g., lattice vacancies, interstitials,and the like) may have “shallow” levels that are inside the forbiddenband gap but near to the valence or conduction bands. Thus the emittedphoton energies can be smaller than the band gap. Further, as electronsand holes are usually delocalized inside semiconductor particles,quantum confinement by nanoparticles (sizes below about 100 nm) can leadto photon emission with energy above the band gap. Suitablesemiconductors and their band gaps, include the following: Amorphoussilicon. Crystalline silicon is an undesirable indirect gap material,but amorphous silicon has similarities to a direct gap material withabsorption edge near 700 nm (about 1.8 eV). (2) III-V compounds:Compounds of Al, Ga, In, with N, P, As, Sb, such as GaAs (1.4 eV), InP(1.3 eV), AlAs (2.1 eV), and InN (0.7 eV). Alloys such as (Ga,Al)As canbe used as well. II-VI compounds: Compounds of Mg, Zn, Cd, with O, S,Se, Te such as CdS (2.5 eV), CdSe (1.7 eV), CdTe (1.5 eV) and theiralloys. And other suitable ternary and quaternary compounds.

In some embodiments, the IR fluorescent pigment is a metal oxide ormetal fluoride, or metal compound, doped with one or more rare earthelements, such as Nd, Pm, Dy, Ho, Er, Tm, or Yb, or a transition metals,such as Cr. In some embodiments, the metal oxide is YAlO₃ (or fluorides)doped with one or more rare earth element, such as Nd, Pm, Dy, Ho, Er,Tm, or Yb, or a transition metals, such as Cr. In some embodiments, themetal oxide is Al₂O₃, Egyptian blue (CaCuSi₄O₁₀), indigo (C₁₆H₁₀N₂O₂),or lazurite (Na₄SSi₄Al₃O₁₂). In some embodiments, the metal oxide is acadmium compound, such as CdS, CdSe, or CdTe. The dopant can be up to(except for “greater than 0%”), or at least, greater than 0%, 0.1%,0.5%, 1%, 5%, 10%, 20%, 30%, 40%, or 50%, or any range between any twovalues thereof, by molar ratio, volume, or weight of the compound. Asuitable dopant is Cr₂O₃.

IR fluorescent pigments suitable for the invention, that are known tofluoresce in the NIR, are Egyptian blue (CaCuSi₄O₁₀, at 910 nm), Hanblue (BaCuSi₄O₁₀), Han purple (BCuSi₂O₆), indigo (used to make bluejeans blue, 750 nm), lazurite (Na₄SSi₃Al₃O₁₂, at 830 nm), and thecadmium compounds Cd(S,Se,Te) (wavelength depends on S/Se/Teproportions). In some embodiments, the metal oxide or a first metaloxide, such as Al₂O₃, is doped with a second metal oxide of an amountranging from greater than 0% to up to 50%. In some embodiments, thesecond metal oxide can be up to (except for “greater than 0%”), or atleast, greater than 0%, 0.1%, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, or 50%,or any range between any two values thereof, by molar ratio, volume, orweight of the compound. In some embodiments, the dopant is Cr₂O₃.Certain oxides are commercially available from Goodfellow Corp.(Coraopolis, Pa.).

Other suitable IR fluorescent pigments include materials that emit inthe near infrared (700 to 1500 nm), such as (Zn, Cd) S: Ag⁺, differentcompositions emit in a band located near 665 up to 725 nm; Zn₃(PO₄)₃:Mn²⁺, 640 nm, really red rather than IR; Al₂O₃: Cr³⁺, 694 nm (deep red);Y₂O₃: Eu, 620, 710 nm; Y₂O₂S: Eu 620, 710 nm; LiAlO₂: Fe³⁺, 743 nm band;InBO₂: Cr, 800 nm; YVO₄: [V]: Nd, wherein [V] means vacancy, 860, 930nm; YAG:Cr, wherein YAG means yttrium-aluminum-gamet, Y₃Al₅O₁₂: Cr³⁺,700 nm; Y₃Ga₅O₁₂: Cr, 700-800 nm; and, Gd₃Ga₅O₁₂: Cr, 700-780 nm.Suitable IR fluorescent pigments are also taught in E. Sluzki, M.Lemoine, and K. Hesse, “Phosphor development for amorphous siliconliquid crystal light valve projection display, J. Electrochem. Soc. 141(11), November 1994. Some specific examples taught by Yen and Websterare shown in Table 1.

TABLE 1 Composition Emission Notes Mg₂SiO₄: Mn²⁺ red, 1.88 eV Mn²⁺associated with deep red emission CaMgSi₂O₆: red, 1.8 eV Eu²⁺, Mn²⁺CaMgSi₂O₇: deep red, Excitation via both Eu²⁺, Mn²⁺ 1.8 eV UV and blueLaPO₄: Eu³⁺ 1.78-2.12 eV Several discrete lines alpha-SrO•3B₂O₃: deepred Broad absorption Sm 1.81 eV 300-550 nm LiAlO₂: Fe³⁺ deep red,requires dopant to 700-800 nm enhance absorption SrMoO₄: U 650-700 nmMg₂TiO₄: Mn⁴⁺ 650-700 nm ZnS: Sn²⁺ 640-760 nm Alloys of ZnS 700-800 nmand CdS doped with Ag⁺, Cl⁻ CaS: Yb²⁺ 750 nm Cl likely co-dopantCaGa₂S₄: Mn²⁺ 710 nm

Other suitable rare earth dopants for near-infrared emission, andsensitizing ions, are taught herein. The sensitizing ions enhanceabsorption of excitation radiant energy and transfer energy to theradiating ions. Selected data from Table IV of G. C. Righini and M.Ferrari, Rivista del Nuovo Cimento, Vol 28, 1-53, (2005) are shown inTable 2.

TABLE 2 Rare earth Emission wavelength(s), dopant ion micrometersSensitizing ions Pr³⁺ 0.89, 1.04, 1.34 Nd³⁺ 0.93, 1.06, 1.35 Cr3³⁺,Mn²⁺, Ce³⁺ Sm³⁺ 0.65 Ho³⁺ 0.55, 1.38, 2.05 Er³⁺ 1.30, 1.54, 1.72, 2.75Cr³⁺, Yb³⁺ Tm³⁺ 0.80, 1.47, 1.95, 2.25 Er³⁺, Yb³⁺ Yb3³⁺ 1.03 Nd³⁺

Y₃Al₅O₁₂:Nd³⁺ is an important laser material that emits at 1060 nm. TheNd³⁺ ion also emits at 1060 nm (a broader line) in a variety of glasses.

The present invention provides for composition comprising metal oxidesor fluorides that fluoresce in the visible or near-infrared. In aparticular embodiment, the metal oxide is ruby powder which can be usedto fabricate a coating. The material is Al₂O₃ with 0.1% Cr₂O₃ and can iscommercially available from Goodfellow Corp. (Coraopolis, Pa.).

In the present invention, the composition has some of the light energythat is absorbed re-radiated by fluorescence. Due to the so-calledStokes shift, re-radiated light usually has a longer wavelength. In someembodiments, the fluorescent energy appears in the NIR, in which has theadvantage of not affecting the color within the visible spectrum, thatis, to the human eye.

UV and VIS photons in the solar spectrum have an average energycorresponding to a wavelength of about 500 nm. The most energetic NIRphotons have a wavelength of about 750 nm. If the quantum efficiency ofthe fluorescence process is about 1 (1 photon out for each photonabsorbed), then the energy yield is about ⅔ (500/750) of the UV/VISinput energy (½ the total). Hence the energy limit for black cited aboveis increased from 0.50 by (0.95) (½) (⅔)=0.317, to about 0.82.

The present invention provides for the use of IR fluorescent pigments topermit various colored materials to remain cooler in the sun than theconventional, non-fluorescent pigments currently in use for thispurpose. One aspect of the invention is that the design of the coatings(and other materials) with specified color must be modified such thatabsorbed energy is not converted to heat, but re-radiated. In someembodiments, the conventional cool pigments are used sparingly.

While IR fluorescent pigments that fluoresce in the visible may be used,it is clear that materials fluorescing in the near-infrared, close to700 nm, are desired. A large number of materials are known as phosphors,for example from applications to cathode ray television screens or aslamp phosphors. It can be appreciated, however, that phosphors that emitin the 700 to about 1000 nm range of particular interest here have beenless-studied since the emitted radiation is not visible. Research onmaterials used for solid state lasers has identified some materials thatemit in the near infrared. Many of these are metal oxides such as YAlO₃(or fluorides) doped with certain rare earths such as Nd, Pm, Dy, Ho,Er, Tm, and Yb. Certain transition metals, such as Cr, are also ofinterest as dopants. IR fluorescent pigments suitable for the invention,that are known to fluoresce in the NIR, are Egyptian blue (CaCuSi₄O₁₀,at 910 nm), indigo (used to make blue jeans blue, 750 nm), lazurite(Na₄SSi₃Al₃O₁₂, at 830 nm), and the cadmium compounds Cd(S,Se,Te)(wavelength depends on S/Se/Te proportions ratio).

In a particular embodiment, the metal oxide is ruby powder (Al₂O₃ dopedwith Cr₂O₃, such as 0.1% Cr₂O₃). The material can be fabricated into asimple film using a transparent binder with a resulting pink color.Spectrophotometer testing show the expected broadband absorption acrossthe UV and VIS spectrum, and very low absorption in the NIR. An increasein the doping to 3% Cr₂O₃ produces a darker red color. To further darkenthe color, the ruby powder can be prepared in the form of nanoparticles(size less than about 50 nm), which would reduce scattering. Theemission wavelength is 694 nm (deep red), with a quantum efficiency of0.7. In some embodiments, a coating with ruby IR fluorescent pigment canalso be darkened by using a polymer medium with higher refractive index,for example, by addition of TiO₂ nanoparticles to the polymer. Rubyemits with a spectrum ranging from 700 to 800 nm.

In some embodiments, the cool-color IR fluorescent pigments aretypically inorganic mixed metal oxides that strongly reflect in the NIR.For example, cool black IR fluorescent pigments can be Cr—Fe—O. Thesolar reflectance of dark cool IR fluorescent pigments range from about0.2 for cool blacks to about 0.4 for greens/blues/reds, falling farshort of our target at least 0.4 for fluorescent cool black and at least0.6 for fluorescent cool dark red.

In some embodiments, the IR fluorescent pigments for useful in buildingenvelopes. Fluorescence in the visible spectrum is commonly used inexisting applications, such as highway signs, where visibility isimportant.

Table 3 below illustrates the potential performance benefits in coatingsof IR fluorescent pigments compared to several industry standardpigments. Specifically, there is dramatically increased Effective SolarReflectance (ESR) of the target dark red compared to a generic ironoxide red and the target dark color pigment compared to generic carbonblack and mixed metal oxide “cool” black pigment. These are thencompared to the performance of rutile TiO₂ white. The ESR is the ratioof outgoing reflected solar radiation to incoming radiation, adjusted toaccount for the extra energy radiated away due to fluorescence.

TABLE 3 Comparison of existing pigments with pigment target values forESR Visible Reflectance Effective Solar (550 nm) Reflectance FluorescentDark Red 0.10 0.60-0.65 Fluorescent Dark Color 0.10 0.40-0.50 RutileTiO₂ White 0.80-0.90 0.70-0.85 Generic Carbon Black 0.05 0.05 GenericIron Oxide Red 0.10 0.20 Generic Mixed Metal 0.08 0.22 Oxide “Cool”Black

Non-limiting examples of suitable IR fluorescent pigments includemetallic pigments, metal oxides, mixed metal oxides, metal sulfides,metal selenides, metal tellurides, metal silicates, inorganic oxides,inorganic silicates, alkaline earth metal silicates. As used herein, theterm “alkaline” refers to the elements of group II of the periodic tableBe, Mg, Ca, Sr, Ba, and Ra (beryllium, magnesium, calcium, strontium,barium, radium). Non-limiting examples of suitable IR fluorescentpigments include metal compounds, which may be doped with one or moremetals, metal oxides, and alkali and/or rare earth elements. As usedherein, the term “alkali” refers to the elements of group I of theperiodic table Li, Na, K, Rb, Cs, and Fr (lithium, sodium, potassium,rubidium, cesium, and francium). As used herein, the term “rare earthelement” refers to the lanthanide series of elements La, Ce, Pr, Nd, Pm,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm and Yb (lanthanum, cerium, praseodymium,neodymium, promethium, samarium, europium, gadolinium, terbium,dysprosium, holmium, erbium, thulium, ytterbium).

Non-limiting examples of IR fluorescent pigments include Egyptian blue(CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀,ruby (Al₂O₃:Cr), Sr(La, Li)CuSi₄O₁₀, and Ba(La, Li)CuSi₄O₁₀. Inparticular, blue alkali earth copper silicates, such as Egyptian blue(CaCuSi₄O₁₀) fluoresce in the 800 to 1200 nm region. Cadmium pigments,such as CdSe, CdTe, and Cd(Se,Te) compounds, and red cadmium pigmentscoated with a zirconium silicate glass, indigo, azurite(Cu₃(CO₃)₂(OH)₂), Ploss blue ((CuCa)(CH₃COO)₂.2H₂O), and smalt(CoO.K.Si) may possess weak fluorescence.

Other non-limiting examples of IR fluorescent pigments may include ZnO,ZnS, ZnSe, ZnTe, (Zn(O,S,Se,Te). These IR fluorescent pigments haveenergy gaps that are too large for band-to-band emission of IR energy,but doping with Sn, Mn, and Te can lead to suitable impurityluminescence. Other non-limiting examples of IR fluorescent pigments mayinclude compounds used in lighting and for fluorescent displays; certaindirect bandgap semiconductors, such as (Al,Ga)As, InP, and the like; andmaterials used for solid state lasers, such as Nd doped yttrium aluminumgarnet, and titanium doped sapphire. In addition, non-limiting examplesof IR fluorescent pigments may include phosphors that emit in the deepred or IR (e.g, LiAlO₂:Fe, CaS:Yb).

The IR fluorescent pigment may absorb visible radiation (380-750nanometers). The absorbed visible radiation may make it such that anindividual sees the coating composition including the IR fluorescentpigment as a color, such as a dark color. Non-limiting examples of darkcolors include black, blue, purple, green, red, and brown.

The IR fluorescent pigments can be added to the coating composition inany suitable form, such as discrete particles, dispersions, solutions,and/or flakes. The IR fluorescent pigments can also be incorporated intothe coatings by use of a grind vehicle, such as an acrylic grindvehicle, the use of which will be familiar to one skilled in the art.

IR Transparent Pigment

The coating composition may also optionally include at least one IRtransparent pigment. As used herein, an “IR transparent pigment” refersto a pigment that is substantially transparent (having the property oftransmitting energy, e.g. radiation, without appreciable scattering inthose wavelengths) in the IR wavelength region (700 nm-1 mm), such as inthe NIR wavelength region (700 to 2500 nanometers), such as is describedin United States Patent Application Publication No. 2004/0191540 at[0020]-[0026], United States Patent Application Publication No.2010/0047620 at [0039], United States Patent Application Publication No.2012/0308724 at [0020]-[0027], the cited portions of which beingincorporated herein by reference. The IR transparent pigment may have anaverage transmission of at least 70% in the IR wavelength region. The atleast one IR transparent pigment can be used to adjust the visible colorof the coating composition, i.e., may be a colorant. The IR transparentpigment may not be transparent at all wavelengths in the IR range butshould be largely transparent in the fluorescent emission wavelength ofthe IR fluorescent pigment.

The IR reflective pigment may reflect radiation at a first wavelengthwhen exposed to radiation comprising fluorescence-exciting radiation,and the IR fluorescent pigment may fluoresce at a second wavelength whenexposed to radiation comprising fluorescence-exciting radiation. Thebalance of the coating composition (i.e. the remaining components of thecoating composition excluding the IR reflective pigment and the IRfluorescent pigment) may be transparent at the first and secondwavelength so as not to adversely affect IR reflection or IRfluorescence or not to affect the visible color of the coatingcomposition.

Film-Forming Resin

The present invention includes a film-forming resin including resinsbased on fluoropolymers (including poly(vinylidene fluoride), PVDF),polyesters, polyacrylates, and/or thermoplastic PVC polymers. As usedherein, a “film-forming resin” refers to a resin that can form acontinuous film on at least a horizontal surface of a substrate uponremoval of any diluents or carriers present in the composition or uponcuring. The film-forming resin can include any of a variety ofthermoplastic and/or thermosetting film-forming resins known in the art.As used herein, the term “thermosetting” refers to resins that “set”irreversibly upon curing or crosslinking, wherein the polymer chains ofthe polymeric components are joined together by covalent bonds. Thisproperty is usually associated with a cross-linking reaction of thecomposition constituents often induced, for example, by heat orradiation. Curing or crosslinking reactions also may be carried outunder ambient conditions or at low temperatures. Once cured orcrosslinked, a thermosetting resin will not melt upon the application ofheat and is insoluble in solvents. As noted, the film-forming resin canalso include a thermoplastic film-forming resin. As used herein, theterm “thermoplastic” refers to resins that include polymeric componentsthat are not joined by covalent bonds and thereby can undergo liquidflow upon heating and are soluble in solvents.

In some non-limiting embodiments, the film-forming resin may include afluoropolymer. The fluoropolymer may include poly(vinylidene fluoride)(PVDF). For example, the film-forming resin may be DURANAR® coating (byPPG Industries, Inc.), such as DURANAR ULTRA-Cool® coatings, DuranarVARI-Cool® coatings, and Duranar GR coatings. The film-forming resin mayinclude CORAFLON® XL fluoropolymer clear coat.

However, any suitable fluoropolymer may be used including the followingexamples: perfluoroalkoxy tetrafluoroethylene copolymer (PFA),ethylenechlorotrifluoroethylene (E-CTFE), ethylenetetrafluoroethylene(E-TFE), poly(vinylidene fluoride) (PVDF), poly(tetrafluoroethylene),poly(vinyl fluoride), poly(trifluoroethylene),poly(chlorotrifluoroethylene) (CTFE), and/or poly(hexafluoropropylene).Mixtures of two or more suitable fluoropolymers can be used, as cancopolymers, terpolymers and the like of suitable fluoropolymers. In oneembodiment of the invention, the fluoropolymer is not a copolymer and/orterpolymer of PVDF and other fluoropolymer(s). It will be appreciatedthat these fluoropolymers are widely commercially available, such as insolid or powder form.

The fluoropolymer is added to a dispersible resin compatible with thefluoropolymer. The dispersible resin can be, for example, waterdispersible or solvent dispersible. Any dispersible resin that iscompatible with the fluoropolymer can be used according to the presentinvention. Suitable dispersible resins include, for example, thosecomprising an acrylic, poly(vinyl acetate), poly(vinyl methyl ketone),polybutadiene and/or poly(urethane). Suitable acrylic monomers includeone or more of t-butylamino methyl (meth)acrylate, (meth)acrylic acid,methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate,hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypropyl(meth)acrylate and mixtures thereof. It will be appreciated that“(meth)acrylate” and like terms refers to both methacrylate andacrylate, as is conventional in the art. In certain embodiments, theresin is a water dispersible acrylic resin having acid functionality. By“water dispersible” is meant that the resin is a polymer or oligomerthat is solubilized, partially solubilized and/or dispersed in somequantity of water with or without additional water soluble solvents. Incertain embodiments, the solution is substantially 100 percent water. Inother embodiments, the solution can be 50 percent water and 50 percentcosolvent, 60 percent water and 40 percent cosolvent, 70 percent waterand 30 percent cosolvent, 80 percent water and 20 percent cosolvent, or90 percent water and 10 percent cosolvent. Suitable cosolvents include,for example, glycol ethers, glycol ether-esters, alcohols, etheralcohols, N-methylpyrrolidone, phthalate plasticizers and/or mixturesthereof. In certain applications, it may be desirable to limit theamount of cosolvent.

The dispersible resin can also be solvent dispersible. A “solventdispersible” resin is a polymer or oligomer that is solubilized in asolvent other than water. Suitable solvents include, but are not limitedto, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, esters,glycols, ethers, ether esters, glycol ethers, glycol ether esters,alcohols, ether alcohols, phthalate plasticizers, N-methyl pyrrolidoneand/or suitable mixtures thereof. Phthalate plasticizers includephthalates esters such as diethylhexyl phthalate, diisononyl phthalate,diisodecyl phthalate, dioctyl phthalate, and butyl benzyl phthalate.

The fluoropolymer can be added or mixed by any means standard in theart, such as by using a Cowles mixer, a media mill, a rotor-stator milland the like, until the desired particle size is achieved. The amount offluoropolymer in the dispersion can range from 30 to 99 weight percent,based on total solid weight of the dispersion.

The fluoropolymer will typically be mixed with the dispersible resinuntil the dispersion is substantially homogenous. The mixture can thenbe dried according to any means known in the art. Particularly suitablemethods for drying are spray drying, tray drying, freeze drying, fluidbed drying, single and double drum drying, flash drying, swirl drying,and numerous other evaporation techniques, the use of all of which willbe familiar to those skilled in the art.

In certain embodiments of the present invention, the dry mixture canthen be ground to a desired particle size. Grinding can be accomplishedby any means known in the art, such as through the use of a classifyingmill. Medium particle sizes of 20 to 50 microns are often desired forcertain applications, such as 30 to 40 microns.

In certain embodiments, a crosslinker can be further added to thedispersion. The crosslinker can be any crosslinker suitable for reactionwith a reactive group on the dispersing resin and/or itself. Thecrosslinker can be in solid or liquid form. Examples includehydroxyalkyl amides, such as those commercially available from EMS asPRIMID, glycidyl functional acrylics, triglycidylisocyanurate,carbodiimides, such as those commercially available from Dow asUCARLINK, melamines, such as those available from Cytec as CYMEL, andblocked isocyanates such as those available from Bayer as CRELAN.

The fluoropolymer may be any fluoropolymer included in U.S. Pat. No.8,030,396, the disclosure of which is hereby incorporated in itsentirety by reference.

The film-forming resin may include polyester polymers. For example, thefilm-forming resin may include DURAFORM® polyester coatings or DURASTAR®polyester coil coatings (by PPG Industries, Inc.). The film-formingresin may include acrylic-based polymers. For example, the film-formingresin may include DURACRON® acrylic-based coatings (by PPG Industries,Inc.). The film-forming resin may include PVC polymers. For example, thefilm-forming resin may include PLASTICRON® PVC coatings (by PPGIndustries, Inc.).

The coating composition(s) described herein can comprise any of avariety of thermoplastic and/or thermosetting compositions known in theart. The coating composition(s) may be water-based or solvent-basedliquid compositions, or, alternatively, in solid particulate form, i.e.,a powder coating.

Thermosetting coating compositions typically comprise a crosslinkingagent that may be selected from, for example, melamines,polyisocyanates, polyepoxides, beta-hydroxyalkylamides, polyacids,anhydrides, organometallic acid-functional materials, polyamines,polyamides, alkoxysilanes, and mixtures of any of the foregoing.

In addition to or in lieu of the above-described crosslinking agents,the coating composition may comprises at least one film-forming resin.Thermosetting or curable coating compositions may comprise film formingpolymers having functional groups that are reactive with thecrosslinking agent. The film-forming resin in the coating compositionsdescribed herein may be selected from any of a variety of polymerswell-known in the art. The film-forming resin can be selected from, forexample, fluoropolymers, polyester polymers, silicone modified polyesterpolymers, acrylic polymers, acrylic latex polymers, vinyl polymers,copolymers thereof, and mixtures thereof. Generally these polymers canbe any polymers of these types made by any method known to those skilledin the art. Such polymers may be solvent borne or water dispersible,emulsifiable, or of limited water solubility. Appropriate mixtures offilm-forming resins may also be used in the preparation of the coatingcompositions described herein.

Non-limiting examples of suitable fluoropolymers film-forming resinsinclude perfluoroalkoxy tetrafluoroethylene copolymer (PFA),ethylenechlorotrifluoroethylene (E-CTFE), ethylenetetrafluoroethylene(E-TFE), poly(vinylidene fluoride) (PVDF), poly(tetrafluoroethylene),poly(vinyl fluoride), poly(trifluoroethylene),poly(chlorotrifluoroethylene) (CTFE), poly(hexafluoropropylene),polymers having alternating fluoroethylene and alkyl vinyl ethersegments (FEVE), and/or mixtures thereof. Non-limiting examples of vinylpolymers film-forming resins include thermoplastic polyvinyl chloride(PVC) polymers. Any dispersible resin that is compatible with thefluoropolymers can be used to prepare dispersions of the fluoropolymerfilm-forming resins. Suitable dispersible resins include, for example,those comprising an acrylic, poly(vinyl acetate), poly(vinyl methylketone), polybutadiene and/or poly(urethane). Suitable acrylic monomersinclude one or more of t-butylamino methyl (meth)acrylate, (meth)acrylicacid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate,hydroxyethyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxypropyl(meth)acrylate and mixtures thereof. It will be appreciated that“(meth)acrylate” and like terms refers to both methacrylate andacrylate, as is conventional in the art. The fluoropolymer can be addedor mixed by any means standard in the art, such as by using a Cowlesmixer, a media mill, a rotor-stator mill and the like, until the desiredparticle size is achieved. The amount of fluoropolymer in the dispersioncan range from 30 to 99 weight percent, based on total solid weight ofthe dispersion. The fluoropolymer will typically be mixed with thedispersible resin until the dispersion is substantially homogenous. Themixture can then be dried according to any means known in the art.Particularly suitable methods for drying are spray drying, tray drying,freeze drying, fluid bed drying, single and double drum drying, flashdrying, swirl drying, and numerous other evaporation techniques, the useof all of which will be familiar to those skilled in the art. The drymixture can then be ground to a desired particle size. Grinding can beaccomplished by any means known in the art, such as through the use of aclassifying mill. Median particle sizes of 20 to 50 microns are oftendesired for certain applications, such as 30 to 40 microns. Acrosslinker can be further added to the dispersion. The crosslinker canbe any crosslinker suitable for reaction with a reactive group on thedispersing resin and/or itself. The crosslinker can be in solid orliquid form. Non-limiting examples include hydroxyalkyl amides, such asthose commercially available from EMS as PRIMID, glycidyl functionalacrylics, triglycidylisocyanurate, carbodiimides, such as thosecommercially available from Dow Chemical Company (Midland, Mich.) asUCARLINK, melamines, such as those available from Cytec as CYMEL, andblocked isocyanates such as those available from Bayer AG (Leverkusen,Germany) as CRELAN.

The film-forming resin can be water dispersible. As used herein, a“water dispersible” resin is a polymer or oligomer that is solubilized,partially solubilized and/or dispersed in some quantity of water with orwithout additional water soluble solvents. The solution can besubstantially 100 percent water. The solution can be 50 percent waterand 50 percent co-solvent, 60 percent water and 40 percent co-solvent,70 percent water and 30 percent co-solvent, 80 percent water and 20percent co-solvent, or 90 percent water and 10 percent co-solvent.Suitable co-solvents include, for example, glycol ethers, glycolether-esters, alcohols, ether alcohols, N-methyl pyrrolidone, phthalateplasticizers and/or mixtures thereof. In certain applications, it may bedesirable to limit the amount of co-solvent.

The film-forming resin can also be solvent dispersible. As used herein,a “solvent dispersible” resin is a polymer or oligomer that issolubilized, partially solubilized and/or dispersed in some quantity ofa solvent other than water. Suitable solvents include, but are notlimited to, aliphatic hydrocarbons, aromatic hydrocarbons, ketones,esters, glycols, ethers, ether esters, glycol ethers, glycol etheresters, alcohols, ether alcohols, phthalate plasticizers. Ketonesinclude isophorone, N-methyl pyrrolidone and/or suitable mixturesthereof. Phthalate plasticizers include phthalates esters such asdiethylhexyl phthalate, diisononyl phthalate, diisodecyl phthalate,dioctyl phthalate, and butyl benzyl phthalate. Appropriate mixtures offilm-forming resins may also be used in the preparation of the presentcoating compositions.

When the coating composition is cured to form a coating and exposed tofluorescence-exciting radiation, the coating may have a greatereffective solar reflectance (ESR) compared to the same coating exposedto the fluorescence-exciting radiation except without the IR fluorescentpigment. Certain methods of measuring solar reflectance fail to detectfluorescence. However, ESR takes into account any benefit of radiationenergy exiting the coating from the fluorescence of a coating. ESR maybe determined by calibrating non-fluorescent samples prepared using amixture of white and black paint on a substrate, such as a metalsubstrate. Solar reflectance may then be plotted against the percent ofblack paint in the white coating. The solar reflectance in this plot maybe determined using a spectrometer. Temperature measurements may then betaken out in the sun and the panel temperature plotted against time.Solar absorptance a of an unknown fluorescent sample may then bedetermined from this information by interpolation. ESR for the unknownfluorescent sample may be determined according to the followingequation: ESR=1−a.

The coating composition, when cured to form a coating and exposed tofluorescence-exciting radiation, may have an ESR of at least 0.25, suchas at least 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8,0.85, 0.9. In addition, a temperature at a time (t₁) after being exposedto the fluorescence-exciting radiation may be lower compared to the samecoating exposed to the fluorescence-exciting radiation except withoutthe IR fluorescent pigment at the time (t₁) after being exposed to thefluorescence-exciting radiation.

The fluorescence exciting radiation may be produced from any suitablesource. Fluorescence-exciting radiation may include sunlight,incandescent light, fluorescent light, xenon light, laser, LED light, ora combination thereof. The fluorescence-exciting radiation may besunlight hitting a building material, such as a roof panel, during asunny day.

The coatings may be prepared by direct incorporation of the dry IRfluorescent pigments and/or the dry IR reflective pigments and/or IRtransparent pigments into the coating. The IR florescent pigments may beadded as a formulated tint designed to optimize pigment dispersionproperties. A salient property of all resins is that they are chosenfrom a group that is largely transparent at the emission wavelength ofthe IR fluorescent pigment.

The IR fluorescent pigments and/or the IR reflective pigments and/or IRtransparent pigments may be incorporated into the coating compositionvia one or more pigment dispersion. As used herein, “pigment dispersion”refers to a composition of pigment in a grinding resin (which may be thesame as or different from the film-forming resin described earlier). Thepigment dispersion may, but does not necessarily need to, include apigment dispersant. The pigment dispersions containing pigment particlesare often milled in a high energy mill in an organic solvent system,such as butyl acetate, using a grinding resin (such as a film-formingresin and/or a pigment dispersant).

The grinding resin is often present in the pigment dispersion in anamount of at least 0.1 percent by weight, such as at least 0.5 percentby weight, or at least 1 percent by weight, based on the total weight ofthe dispersion. The grinding resin is also often present in the pigmentdispersion in an amount of less than 65 percent by weight, or less than40 percent by weight, based on the total weight of the dispersion. Theamount of grinding resin present in the pigment dispersion may rangebetween any combinations of these values, inclusive of the recitedvalues.

The film-forming resin can comprise at least 0.05 weight %, at least 0.1weight %, at least 0.5 weight %, or at least 1 weight %, based on thetotal solids weight of the composition. The film-forming resin cancomprise up to 90 weight %, up to 70 weight %, or up to 60 weight %,based on the total solids weight of the composition.

The IR fluorescent pigments can comprise at least 0.05 weight %, atleast 0.1 weight %, at least 0.5 weight or at least 1 weight %, based onthe total solids weight of the composition. The IR fluorescent pigmentscan comprise up to 50 weight %, up to 40 weight %, or up to 30 weight %,based on the total solids weight of the composition.

The IR reflective pigments can comprise at least 0.05 weight %, at least0.1 weight %, at least 0.5 weight or at least 1 weight %, based on thetotal solids weight of the composition. The IR reflective pigments cancomprise up to 50 weight %, up to 40 weight %, or up to 30 weight %,based on the total solids weight of the composition.

The IR fluorescent pigments have an average particle size of no morethan 10 microns, no more than 1 micron, or no more than 750 nm. Inparticular, the IR fluorescent pigments may have an average particlesize of from 50 nm to 10 microns. In particular, the IR fluorescentpigments may have an average particle size of from 100 nm to 1 micron,such as from 500 nm to 750 nm. A dispersion containing the IRfluorescent pigments is substantially free of pigments having an averageparticle size of more than 10 microns, no more than 1 micron, or no morethan 750 nm. By “substantially free” it is meant that no more than 10%by weight, such as no more than 5% by weight, or no more than 1% byweight, of the IR fluorescent pigments present in the dispersion have anaverage particle size of more than 10 microns, no more than 1 micron, orno more than 750 nm. The IR reflective pigments have an average particlesize of no more than 10 microns, no more than 1 micron, or no more than750 nm. A dispersion containing the IR reflective pigments aresubstantially free of pigments having an average particle size of morethan 10 microns, no more than 1 micron, or no more than 750 nm.

The present invention is further directed to methods for preparingcoatings comprising blending a first dispersion of the film-formingresin and a second dispersion comprising one or more IR fluorescentpigments. The second dispersion may also comprise one or more IRreflective pigments and optionally one or more IR transparent pigments.Alternatively, the method may also comprise blending into the first andsecond dispersion blends a third dispersion comprising one or more IRreflective pigments and/or one or more IR transparent pigments. Thefinal dispersion blend may then be dried. If desired, the dried blendcan then undergo grinding. The drying and grinding are as describedabove. Blending can be done by any means known in the art, such asmixing with a low shear mixer or by shaking. One or both dispersions canbe automatically dispensed from a computerized dispensing system. Forexample, to a first film-forming resin dispersion can be added a secondpigment dispersion, or a combination of second pigment dispersion(s) andthird pigment dispersion(s) to achieve the desired color. The correctamount and type of second and third pigment dispersion(s) to add to thefilm-forming resin dispersion can be determined, for example, by use ofcolor matching and/or color generating computer software known in theart.

The first dispersion of the film-forming resin may comprisefluoropolymers, polyesters, polyacrylates, and/or thermoplastic PVCpolymers.

The second dispersion comprising an IR fluorescent pigment (andoptionally an IR reflective pigment and/or IR transparent pigment) cancomprise the same dispersible resin as the first dispersion, or adifferent dispersible resin. If different dispersible resins are used,they should be selected so as to be compatible both with each other.Both the first and second dispersions can be water based, or both can besolvent based, or one can be water based and one can be solvent based.“Water based” means that the dispersion includes a water dispersibleresin; “solvent based” means that the dispersion includes a solventdispersible resin. The water-based dispersion can include a limitedamount of water-soluble solvents to improve application and film formingperformance.

The third dispersion comprising an IR reflective pigment and/or IRtransparent pigment can comprise the same dispersible resin as the firstand/or second dispersion, or a different dispersible resin. If differentdispersible resins are used, they should be selected so as to becompatible both with each other, and with the film-forming resin. Thefirst, second, and third dispersions can be water based, or they can besolvent based, or one or two can be water based and one or two can besolvent based. “Solvent based” means that the dispersion includes asolvent dispersible resin.

The IR fluorescent pigment(s), and/or IR reflective pigment(s), and/orIR transparent pigment(s) can be added to the dispersion(s) in the samemanner as the reactants that form a polymer in the film-forming resin.The amount of colorant in the dispersion can be any amount that impartsthe desired color, such as from 0.5 to 50 weight percent, based on thetotal weight of the reactants.

As described above, any of the dispersions can be water-based.Similarly, the medium of any of the dispersions can be substantially 100percent water, or can be 50 percent water and 50 percent co-solvent, 60percent water and 40 percent co-solvent, 70 percent water and 30 percentco-solvent, 80 percent water and 20 percent co-solvent, or 90 percentwater and 10 percent co-solvent, as described above.

It may be desired to partially or wholly neutralize any acidfunctionality on the film-forming resin. Neutralization can assist inthe preparation of a water based dispersion. Any suitable neutralizingagent can be used, such as triethyl amine, triethanol amine, dimethylethanolamine, methyl diethanolamine, diethyl ethanolamine, diisopropylamine, and/or ammonium hydroxide.

It may also be desirable to include a crosslinker in either or both ofthe dispersions. Any of the crosslinkers described above can be used.

It may be desirable to ensure that the proper spectral response and/orcolor for the coating is achieved. This can be done by doing, forexample, a drawdown or spray out of the blended dispersions to see ifthe appropriate spectral response and/or color is obtained. If not, moreof the pigment dispersion(s) or more of the film-forming resindispersion can be added to adjust the color accordingly. The adjustedblend can then be dried, or it can be further tested to confirm that thedesired color is achieved.

The coating composition may further include a colorant. The colorant mayinclude further pigments, dyes, tints, including but not limited tothose used in the paint industry and/or listed in the Dry ColorManufacturers Associate (DCMA) as well as special effect compositions. Acolorant may include, for example, a finely divided solid powder that isinsoluble but wettable under the conditions of use. A colorant may beorganic or inorganic and can be agglomerated or non-agglomerated. Thecolorant can be in the form of a dispersion including, but not limitedto, a nanoparticle dispersion. Nanoparticle dispersions can include oneor more highly dispersed nanoparticle colorants or colorant particlesthat produce a desirable visible color and/or opacity and/or visualeffect. Nanoparticle dispersions can include colorants such as pigmentsor dyes having a particle size less than about 150 nm, such as less than70 nm, or less than 30 nm.

Any additives standard in the coatings art can be added to any of thedispersions described above. This includes, for example, fillers,extenders, UV absorbers, light stabilizers, plasticizers, surfactants,wetting agents, defoamers and the like. In formulating the dispersionsdescribed above, it may also be desirable to add additional dispersibleresins the same as or compatible with that in which either of thepigment or film-forming resin polymer is dispersed in order to adjustthe level of film-forming resin polymer or pigment.

The present invention is also directed to a substrate at least partiallycoated with a coating prepared from the coating composition including atleast one IR fluorescent pigment, IR reflective pigment, optional IRtransparent pigment, and film-forming resin based on fluoropolymers,polyester polymers, silicone modified polyester polymers, acrylicpolymers, acrylic latex polymers, vinyl polymers, copolymers thereof,and mixtures thereof. In non-limiting examples, the coating compositioncan be applied to the substrate as a topcoat or an undercoat. It shouldbe understood that the use of coatings containing IR fluorescent and IRreflective pigments may require that any additional coatings applied ontop of the coatings containing IR fluorescent and IR reflective pigmentsshould absorb very weakly in the IR, not absorb in the IR and/or if thecoatings are colored, contain IR transparent pigments.

The coating compositions described above are also suitable for use in,for example, multi-component composite coating systems, for example, asa primer coating or as a pigmented base coating composition in acolor-plus-clear system, or as a monocoat topcoat. The foregoing coatingcompositions can be used to form a topcoat in a multi-componentcomposite coating system that further comprises an IR reflective coatinglayer underlying at least a portion of the topcoat. As will beappreciated, various other coating layers may be present as previouslydescribed, such as, for example, a colorless clearcoat layer which maybe deposited over at least a portion of the topcoat. In addition, one ormore coating layers may be deposited between the topcoat and the IRreflective coating layer underlying the topcoat, optionally with thesecoatings not absorbing in the IR. Moreover one or more coating layersmay be deposited between the substrate and the IR reflective coatinglayer underlying at least a portion of the topcoat, such as, forexample, various corrosion resisting primer layers, including, withoutlimitation, electrodeposited primer layers as are known in the art. Theclear coat may be designed to further improve durability of the IRfluorescent coating, such as resistance to UV propagated tophotooxidation.

A multi-layer coating may include a first coating layer including acured IR reflective coating composition. A second coating layer mayoverlay at least a portion of the first coating layer, and the secondcoating layer may be the coating composition including the film-formingresin, IR reflective pigment, and IR fluorescent pigment. The firstcoating layer, being an IR reflective coating, may reflect thefluorescence exhibited by the IR fluorescent pigment of the secondcoating layer away from the coated substrate.

The substrate upon which the coatings (e.g., the cured coatingcomposition or the multi-layer coating) described above may be depositedmay take numerous forms and be produced from a variety of materials. Thecoating composition of the present invention can be applied to buildingsubstrates, such as exterior panels and roofing materials, industrialsubstrates, and the like. These substrates can be, for example, metallicor non-metallic. Metallic substrates include, but are not limited to,foils, sheets, or workpieces constructed of cold rolled steel, stainlesssteel and steel surface-treated with any of zinc metal, zinc compoundsand zinc alloys (including electrogalvanized steel, hot-dippedgalvanized steel, GALVANNEAL steel, and steel plated with zinc alloy),copper, magnesium, and alloys thereof, aluminum alloys, zinc-aluminumalloys such as GALFAN™, GALVALUME™, aluminum plated steel and aluminumalloy plated steel substrates may also be used. Steel substrates (suchas cold rolled steel or any of the steel substrates listed above) coatedwith a weldable, zinc-rich or iron phosphide-rich organic coating arealso suitable. The metallic substrates can also further comprise a metalpretreatment coating or conversion coating. Non-limiting examples ofsuitable pretreatment coatings or conversion coatings include, but arenot limited to, zinc phosphate, iron, phosphate, or chromate-containingpretreatments. Other non-limiting examples of suitable pretreatmentcoatings or conversion coatings include, but are not limited to,thin-film pretreatment coatings such as a zirconium ortitanium-containing pretreatment. The metal pretreatment coating canalso include a sealer, such as a chromate or non-chromate sealer.Non-metallic substrates may be polymeric including plastic, polyester,polyolefin, polyamide, cellulosic, polystyrene, polyacrylic,poly(ethylene naphthalate), polypropylene, polyethylene, nylon, EVOH,polylactic acid, other “green” polymeric substrates,poly(ethyleneterephthalate) (PET), polycarbonate, polycarbonateacrylonitrile butadiene styrene (PC/ABS), polyamide, or may be wood,veneer, wood composite, particle board, medium density fiberboard,cement, stone, glass, paper, cardboard, textiles, leather, bothsynthetic and natural, and the like. Non-metallic substrates may alsoinclude a treatment coating that is applied before application of thecoating, which increases the adhesion of the coating to the substrate.

The state of the art in building envelopes requires consideration of anumber of market segments. In general, the market is divided into slopedand low-sloped roofs. The current state-of-the-art for flat orlow-sloped roofs is a white roof, which can have initial solarreflectance values on the order of 0.70-0.85. Once a white roof issoiled, the typical solar reflectance is between 0.55 and 0.65. In someembodiments of the present invention, the coatings have the aestheticsof dark colors with the performance of the white roofs that areacceptable for low-sloped roofs.

The current state-of-the-art for steep roofs is cool spectrallyselective solutions for most applications. For light colors, the use ofexisting technology in NIR reflective coatings achieves a solarreflectance of 25% to 50% depending on the color. In some embodiments ofthe present invention, dark color IR fluorescent pigments are providedthat achieve ESR values meeting or exceeding the values for the state ofthe art in light colors.

Certain organic IR fluorescent pigments have properties that would beattractive for steep roofs such as high hiding power (the amount of IRfluorescent pigment required in a coating to achieve color strength) andlow NIR absorptance. However organic IR fluorescent pigments use islimited because they lack UV durability. By-and-large, organic IRfluorescent pigments are seldom used for building materials exposed tothe environment due to durability issues.

In some embodiments, the composition can coat metal objects, such ascoiled metal products (i.e. metal roofs). The novel dark color IRfluorescent pigments can convert a significant fraction of the absorbedvisible spectrum energy into NIR fluorescence.

The present invention has a variety of uses. It can be used for roofingand siding materials for construction in warm and hot climates. Also,for many other situations where white is not a desired color and solarheating is undesired, such as for auto finishes, PVC piping clothing,etc. Cool roofing materials have the advantage of generally providingfor reduced air conditioning costs and improved comfort in warm and hotclimates, lowered outside air temperatures (reducing smog), and areduction in global warming.

The present invention can be made using techniques known to one skilledin the art. Most roofing and siding materials are routinely fabricatedwith colorants (pigments) to provide an attractive appearance. The useof IR fluorescent pigments is quite similar to the use of conventionalpigments. Coating and materials design issues are durability, resistanceto acids and bases, toxicity (in some cases), potential to react withH₂O, CO₂, O₂, etc. In some cases coatings on the IR fluorescent pigmentparticles may be used to make the IR fluorescent pigments more durable(e.g., slow down reactions with water vapor), or to protect polymericmaterials from photo-induced damage (e.g., coatings on generic TiO₂white pigment), or to avoid leaching of toxic chemicals (e.g., cadmiumfrom CdS, CdSe. CdTe). Where IR fluorescent pigments are used withco-pigments, it is important to minimize absorption of photons thatwould otherwise excite the fluorescent pigments.

Most of the usual techniques for coloration of conventional roofing andsiding materials can be used. These include pigmented silicate coatingsused on roofing granules employed on asphalt shingles. Metal roofinguses pigments in polymeric coatings. For concrete and clay roofing tilespigmented top coatings can be used or the pigment can be dispersedthrough the body of the tile. For roof coatings applied on site andsingle-ply membranes the pigment is dispersed in the top layer.

The coating compositions from which each of the coatings described aboveis deposited can be applied to a substrate by any of a variety ofmethods including dipping or immersion, spraying, intermittent spraying,dipping followed by spraying, spraying followed by dipping, brushing, orroll-coating, among other methods. The coating compositions may beapplied by roll-coating and, accordingly, such compositions often have aviscosity that is suitable for application by roll-coating at ambientconditions. In particular, for roll coating applications, coatingcompositions with film-forming resins including fluorocarbonsconventionally may contain isophorone and/or cyclohexanone as solvents.

After application of a coating composition to the substrate, it isallowed to coalesce to form a substantially continuous film on thesubstrate. As used herein, “coalescence” refers to the process by whichsolvents are removed prior to curing. During the curing, the polymer maycrosslink with a crosslinker at temperatures ranging from ambienttemperatures to high temperatures. “Ambient temperatures,” for thepurposes of the present invention, include temperatures from about 5° C.to about 40° C. Typically, the film thickness will be 0.01 to 150 mils(about 0.25 to 3000 microns), such as 0.01 to 5 mils (0.25 to 127microns), or 0.1 to 2 mils (2.54 to 50.8 microns) in thickness. A methodof forming a coating film includes applying a coating composition to thesurface of a substrate or article to be coated, coalescing the coatingcomposition to form a substantially continuous film and then curing thethus-obtained coating. Curing of these coatings can comprise a flash atambient or elevated temperatures followed by a thermal bake. Curing canoccur at ambient temperature of 20° C. to 250° C., for example.

Any of the coating compositions described herein can include additionalmaterials. Non-limiting examples of additional materials that can beused with the coating compositions of the present invention includeplasticizers, abrasion resistant particles, corrosion resistantparticles, corrosion inhibiting additives, fillers including, but notlimited to, clays, inorganic minerals, anti-oxidants, hindered aminelight stabilizers, UV light absorbers and stabilizers, surfactants, flowand surface control agents, thixotropic agents, organic co-solvents,reactive diluents, catalysts, reaction inhibitors, and other customaryauxiliaries. The coatings compositions of the present application may beused in any coating design for any durable exterior application.

A method of reducing the temperature of an article may include applyinga coating composition to at least a portion of a surface of an article,the coating composition comprising (i) a film-forming resin, (ii) an IRreflective pigment, and (iii) an IR fluorescent pigment different fromthe IR reflective pigment. The method also includes curing the coatingcomposition to form a coating on the article. When the coatingcomposition is cured to form a coating and exposed tofluorescence-exciting radiation, the coating has a greater effectivesolar reflectance (ESR) compared to the same coating exposed to thefluorescence-exciting radiation except without the IR fluorescentpigment. The article may be any of the previously described substrates,such as a building substrate. The coating composition may be any of thepreviously described coating compositions or the previously describedmulti-layer coating may coat the article.

The following examples are presented to demonstrate the generalprinciples of the invention. The invention should not be considered aslimited to the specific examples presented. All parts and percentages inthe examples are by weight unless otherwise indicated.

Example 1 Synthesis of Red Pigments Via Combustion Synthesis andAnalyses

Samples of Al2O3(4 g, 16 g, and 200 g) doped with 1 wt % Cr2O3 or 3 wt %of Cr2O3 were synthesized via a combustion synthesis method. Analyticaltesting was conducted on two samples of dark red pigments Al₂O₃ dopedwith 1 wt % Cr2O3 and Al₂O₃ doped with 3 wt % of Cr2O3. X-rayfluorescence (semi-quantitative) indicated that the elementalcompositions of the pigments were close to their expected values. X-raydiffraction XRD patterns of the two samples showed the presence ofα-Al2O3, which is the desired phase of Al2O3 for NIR fluorescence. Inaddition, the narrow peaks in the XRD patterns suggested the presence oflarge crystalline particles (FIG. 1 ). Scanning electron microscopy(SEM) was employed to observe the particle size and morphology of thepigment samples prepared by combustion synthesis (FIG. 2 , micrographB). Micrographs indicated the presence of large particles (FIG. 2 ,micrograph A). During the combustion synthesis of the dark red pigments,a green byproduct (γ-alumina) was formed and removed. In addition, thepigments obtained from the combustion synthesis procedure were pink.These pigments become redder as the particle size is increased. Highresolution spectral reflectance measurements showed a sharp absorptiondoublet at fluorescence wavelengths of 692.7 and 694.0 nm.

Example 2 Testing Methods

Three calibration panels (whose spectral reflectance values weremeasured using a Perkin Elmer Lamda 900 UV-Vis-NIR spectrometer) wereplaced onto a support along with an experimental sample. The surfacetemperatures were measured with an IR thermometer and plotted versustime. The effective solar absorptance for the experimental sample wasinterpolated from the solar absorptance values for the calibratedsamples. The effective solar reflectance (ESR) was then calculated usingthe formula: ESR=1−effective solar absorptance (a).

FIG. 3 shows a plot of the temperature rise when all of the standardreference samples are used at the same time. These measurements weretaken on a clear summer day, near noon. They show that the sunlittemperature, as a function of spectrometer-measured solar absorptance a,is slightly non-linear. This shows that the basic function oftemperature vs. absorptance a has negative curvature.

Measurement of the fluorescence of the pigments and pigmented coatingswas performed using a NIR spectrofluorometer, which was equipped with anInGaAs detector (capable of measurements from 500-1700 nm). Severalmeasurements were conducted on Cr:Al₂O₃ and Egyptian blue (CaCuSi₄O₁₀)pigments. FIG. 4 shows the fluorescence spectra for 3 wt % Cr₂O₃ dopedAl₂O₃ pigments excited at 500 nm and FIG. 5 shows the fluorescencespectra for Egyptian blue pigments excited at 600 nm.

FIGS. 6A and 6B are graphs showing the fluorescence spectra of coatingsover white substrate pigmented with 500 g/m² of 0 to 4 wt % Cr₂O₃ dopedAl₂O₃. The nominal 0% pigment contains a trace of Cr. The spectra wereobtained with a spectrofluorometer based on a 150 mm Spectralonintegrating sphere and a miniature monochromator with a silicon arraydetector. A monochromator from Ocean Optics (Dunedin, Fla.) was refittedwith a new diffraction grating, a narrower slit and a new silicon arraydetector.

Example 3 Coatings Including Red Pigment

Coatings based on PVDF including 500 g/m² of Al₂O₃ doped with Cr₂O₃pigments were synthesized via the combustion process described above(particle size of several microns). These coatings had a reflectance of0.31 at 550 nm. Thinner coatings with 100 g/m² of Al₂O₃ doped with Cr₂O₃synthesized via the combustion process described above had a reflectanceof 0.38 at 550 nm.

Additionally, Al₂O₃ doped with 1.5 wt % and 4.5 wt % Cr₂O₃ pigments withan average particle size of 650 nm were prepared. Egyptian blue pigmentswere also prepared with an average particle size of 650 nm. Thesepigments were included into a coating based on a PVDF film-formingresin. Effective solar reflectance (ESR) measurements were made on thecoatings made using these pigments and are shown in Table 4. Thesubstrates utilized for the evaluation of the coatings were aluminumsubstrates coated with a yellow chrome primer.

TABLE 4 ESR measurements for samples Spectrometer (air mass 1,Spectrometer Pigment included in coating ESR global spectrum) (550 nm)Al₂O₃ doped pigment 0.576 0.580 0.57 (1% Cr₂O₃) Al₂O₃ doped pigment0.542 0.554 0.46 (4.5% Cr₂O₃) Egyptian blue 0.470 0.466 0.50

Example 4 NIR Spectra of Coatings Including Blue, Purple, Yellow, Orangeand Red Pigments

Alkali earth copper silicate pigments including Egyptian blue(CaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀ as well as BaCuSi₄O₁₀and SrCuSi₄O₁₀ with lithium and lanthanum as co-dopants, were evaluatedfor NIR fluorescent properties. Egyptian blue (CaCuSi₄O₁₀ emits from 900to 1000 nm. Egyptian blue was incorporated into a coating formulationbased on a PVDF film-forming resin at 0.14 and 0.4 pigment to binder(P:B) ratios. FIG. 7 shows the fluorescence spectra of (a) an Egyptianblue pigment (bold solid line), (b) a 0.14 P:B Egyptian blue coatingover chrome primed aluminum substrate (light solid line) and (c) a 0.4P:B Egyptian blue coating over chrome primed aluminum substrate (bolddashed line). The excitation wavelength for all samples was 600 nm. FIG.8 shows the emission spectra of Egyptian blue and Han purple (BaCuSi₂O₆)coatings based on an acrylic paint over a white substrate.

Han blue (BaCuSi₄O₁₀ and the alkali earth metal (SrCuSi₄O₁₀ with lithiumand lanthanum as co-dopants showed NIR fluorescent properties.Additionally, cadmium pigments, CdSe and CdTe reagents, a “zirconia” red(a red cadmium pigment coated with a zirconium silicate glass), indigo,blue verditer, copper blue, azurite (Cu₃(CO₃)₂(OH)₂), Ploss blue((CuCa)(CH₃COO)₂.2H₂O), and smalt blue (CoO.K.Si) were prepared. Thesepigments did not show NIR fluorescence during testing, ruling out strongfluorescence but not weak fluorescence. In particular, cadmium pigments(alloys of CdS and CdSe with colors ranging from yellow, to orange, tored, and black) are direct gap semiconductors that do fluoresce (M.Thoury, et al. Appl. Spectroscopy 65, 939-951 (2011)), and nanoparticlesof CdSe have exhibited quantum efficiencies as high as 0.8 (P. Reiss, etal., Nano Letters 2, 781-784 (2002)).

Example 5 Reflectance Measurements of Non-Fluorescent Pigments

FIG. 9 shows a graph of the reflectance of five cadmium pigments,commercially available as artist paints, of formula CdS_(1-x) Se_(x)with x=0 for yellow to x almost equal to 1 for dark red. As FIG. 9indicates, as x increases, the absorption edge shifts to a longerwavelength. FIG. 10 shows a graph of the reflectance of three cadmiumpigments (dark red, medium red, and light red) and a zirconia redpigment, commercially available from Kremer Pigment Inc. (New York,N.Y.). These reflectance measurements indicate that, even withoutfluorescence, the cadmium pigments are “cool” (IR reflective), with asharp transition from absorptive to reflective at their semiconductingband edges, shown in FIG. 9 and FIG. 10 .

Solar reflectance was tested according to the air-mass 1 globalhorizontal (AM1GH) solar reflectance (SR) test using a standard solarreflectance spectrum that corresponds to a clear day with the sunoverhead (R. Levinson, H. Akbari, and P. Berdahl, “Measuring solarreflectance—part I: defining a metric that accurately predicts solarheat gain,” Solar Energy 84, 1717-1744 (2010)).

FIG. 11 shows a graph of the spectral reflectance of smalt blue(CoO.K.Si), a cobalt potassium silicate glass, as compared to thespectral reflectance of Egyptian blue (CaCuSi₄O₁₀). FIG. 11 shows a verysharp transition from absorptive to reflective right at 700 nm. Thereflectance measurement with respect to Egyptian blue over a whitesubstrate shows some absorption in the 700 to 1100 nm range.

Cadmium yellow, orange, and red pigments were measured for theirfluorescence and they all demonstrated some level of NIR fluorescence.CdSe nanoparticles showed some fluorescence behavior, most notably atabout 850-1300 nm for two cadmium pigments having a deep red color.

Example 6 Physical Characterization of Cr₂O₃ Doped Al₂O₃Pigments

Two samples of Cr₂O₃ doped Al₂O₃ with different particle sizes andlevels of chromium (1.5 wt % Cr₂O₃ and the other was 4.5 wt % Cr₂O₃)were analytically tested (microscopy, particle size, and elementalcomposition). The two pigments contained different levels of chromium asevidenced by the elemental data (x-ray fluorescence). The two pigmentswere evaluated for their NIR fluorescence behavior, which indicated thatthe 1.5 wt % Cr₂O₃ doped Al₂O₃ displayed a more intense fluorescencethan the 4.5 wt % Cr₂O₃ doped Al₂O₃.

FIG. 2 shows scanning electron micrographs of the 1% Cr₂O₃ doped Al₂O₃pigment (Micrograph A) and the 3% Cr₂O₃ doped Al₂O₃(Micrograph B). Theparticle size for the 3% Cr₂O₃ doped Al₂O₃ pigment was much smaller (650nm) than the 1% Cr₂O₃ doped Al₂O₃ (several microns).

Example 7 Spectroscopy Data for Alkali Earth Copper Silicate Pigments inDifferent Types of Coatings

Table 5 lists alkali earth copper silicate pigments that were tested forNIR fluorescence.

TABLE 5 Alkali earth copper silicate pigments Chemical formula Commonname BaCuSi₂O₆ Han purple CaCuSi₄O₁₀ Egyptian blue SrCuSi₄O₁₀ —BaCuSi₄O₁₀ Han blue Sr(La, Li)CuSi₄O₁₀ — Ba(La, Li)CuSi₄O₁₀ —

FIG. 12 shows the NIR fluorescence spectra of several alkali earthcopper silicate pigments (excitation wavelength of 600 nm). Ruby (1.5 wt% Cr₂O₃ doped Al₂O₃) was included for comparison (excitation wavelengthof 550 nm). Ba(La,Li)CuSi₄O₁₀ and Sr(La,Li)CuSi₄O₁₀ NIR fluorescencespectra were measured for small and large particle sizes.

Four coatings based on two pigments Ba(La,Li)CuSi₄O₁₀ (small particles)and SrCuSi₄O₁₀ (large particles) in two film-forming resins (onecontaining PVDF and the other being acrylic-based) were evaluated. Table6 shows the solar reflectance (AM1GH and ESR), benefit fromfluorescence, reflectance, and substrate of these four coatings in afilm-forming resin containing PVDF over a yellow substrate and a whitesubstrate. Benefit from fluorescence is the difference between AM1GH andESR solar reflectance, indicating the contribution of fluorescence tothe solar reflectance. Table 7 shows the solar reflectance (AM1GH andESR), benefit from fluorescence, reflectance, and substrate of thesefour coatings in an acrylic film-forming resin over a white substrate.

TABLE 6 Spectroscopy data for Ba(La, Li)CuSi₄O₁₀ (small particles) andSrCuSi₄O₁₀ (large particles) in a film-forming resin containing PVDFSolar Solar Benefit Pigment in reflectance reflectance from ReflectancePVDF coating (AM1GH)¹ (ESR)² fluorescence (550 nm)³ Substrate Ba(La,Li)CuSi₄O₁₀ 0.442 0.447 0.005 0.365 Yellow⁴ (small particles) Ba(La,Li)CuSi₄O₁₀ 0.573 0.621 0.048 0.485 White⁵ (small particles) SrCuSi₄O₁₀0.434 0.446 0.012 0.349 Yellow⁴ (large particles) SrCuSi₄O₁₀ 0.605 0.6490.044 0.510 White⁵ (large particles) ¹AM1GH refers to the solar spectrumused to tabulate the solar reflectance from the spectrometer data. ²TheESR (Effective Solar Reflectance) is obtained from temperaturemeasurements in sunlight. ³The reflectance at 550 nm is a measure ofvisual brightness. ⁴Yellow chrome primer over aluminum substrate.Appearance is green with a blue overcoat. ⁵White primer over yellowchrome primed aluminum substrate.

TABLE 7 Spectroscopy data for Ba(La, Li)CuSi₄O₁₀ (small particles) andSrCuSi₄O₁₀ (large particles) in an acrylic film-forming resin containingPigment in Solar Solar Benefit Pigment acrylic-based reflectancereflectance from Reflectance amount coating (AM1GH)¹ (ESR)² fluorescence(550 nm)³ Substrate (g/m2)⁴ Ba(La, Li)CuSi₄O₁₀ 0.361 0.436 0.075 0.192Bright 160 (small particles) white SrCuSi₄O₁₀ 0.405 0.498 0.093 0.173Bright 100 (large particles) white ¹AM1GH refers to the solar spectrumused to tabulate the solar reflectance from the spectrometer data. ²TheESR (Effective Solar Reflectance) is obtained from temperaturemeasurements in sunlight. ³The reflectance at 550 nm is a measure ofvisual brightness. ⁴Amount of pigment per unit area.

FIG. 13 shows the plots of spectral reflectance for PVDF-type coatingscontaining Ba(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (largeparticles) over white and yellow substrates. FIG. 14 shows the plots ofspectral reflectance for acrylic-based coatings containingBa(La,Li)CuSi₄O₁₀ (small particles) and SrCuSi₄O₁₀ (large particles)over white substrates. FIG. 15 shows the reflectance of the yellowprimer and the white-coated substrates used as the underlayer for thecoatings of FIGS. 13 and 14 .

FIG. 16A shows the fluorescence from several samples includingSrCuSi₄O₁₀ (large particle size) as compared to Egyptian blue. The twotop curves (SrCuSi₄O₁₀ (Large) (100 g/m²) over white and SrCuSi₄O₁₀(Large) (50 g/m²) over white) show that increased pigment amount yieldsmore fluorescence. FIG. 16B shows the fluorescence for samples includingBa(La,Li)CuSi₄O₁₀ (small). FIG. 16C shows the reflectance data thatcorresponds to FIGS. 16A and 16B. FIG. 16D shows the fluorescence of astrontium compound doped with equal amounts of La and Li, compared withan undoped material. FIG. 16E shows the reflectance data correspondingto FIG. 16D. FIG. 16F shows the fluorescence data on a BaCuSi₄O₁₀ samplethat is contaminated with CuO. FIG. 16G shows the reflectance datacorresponding to the fluorescence plot of FIG. 16F. The spectra in thevisible region show that before washing, the color is gray, and afterwashing the color is blue. FIG. 16H shows the fluorescence of someEgyptian blue samples. 16I shows the reflectance data corresponding toFIG. 16H.

Example 8 Ratios of Pigment to Film-Forming Resin and Film Thickness

The effect of pigment loading level and the effect of film thickness (ata given pigment to binder (P:B) ratio) on fluorescence intensity wereevaluated. A pigment to binder ladder ranging from 0.2 P:B to 0.8 P:Band film thickness ladders for each P:B ratio ranging from one to threecoats were coated over an aluminum substrate coated with a yellow chromeprimer and a white primer. 3% Cr₂O₃ doped Al₂O₃ pigment (small particles650 nm) was incorporated into a PVDF-based coating system during thedispersion phase of paint making. The color of the coatings was pink.Test coatings were prepared over yellow chrome primed substrates. FIG.17 shows nine fluorescence spectra corresponding to coatings with threeP:B ratios (0.2, 0.4, and 0.8) and three film thicknesses (1 coat, 2coats, 3 coats) for each coating. The intensity of the fluorescenceincreases with increasing P:B ratio and film thickness.

These coatings and additional coatings (3% Cr₂O₃ doped Al₂O₃ coatingsover yellow primer, Egyptian blue, Han blue and Han purple) were alsoevaluated for ESR measurements in the sun. ESR may also be expressed interms of the effective solar absorptance, a according to the followingequation a=1−ESR. FIG. 18 shows the temperature measurements for 18samples (1.5% Cr₂O₃ doped Al₂O₃ pigment with P:B ratios of 0.2, 0.4, and0.8 and 1, 2, and 3 coats film thickness, 1.5% Cr₂O₃ doped Al₂O₃coatings over yellow primer, Egyptian blue pigment with P:B ratios of0.4 and 0.8; Han blue pigment with P:B ratios of 0.4 and 0.8; Han purplepigment with P:B ratios of 0.4 and 0.8), and also for 4 gray-scalestandards. The resulting values are plotted versus the a-values fromspectrometer spectral reflectance measurements. Linear least square fitlines are given for the calibration samples (bold line), and for thetested samples. The two lines are parallel, but are shifted from oneanother by about 0.5° C. FIG. 18 shows the temperature differences abovethe ambient temperature for these 18 samples and the 4 calibratedstandards. The ESR values are obtained by using the sample temperaturesto determine the solar absorption the calibration samples would requireto come to the same temperature. From the cluster of coolest samples,the difference in temperatures is about 2.5° C., which may be due to thea-values of the samples and/or due to fluorescence. It is estimated thatabout 0.8° C. is due to a-values, and 1.7° C. is due to fluorescence.Using the slope of the curve, a contribution of roughly 0.04 to the a(and ESR) comes from fluorescence.

To assign temperature-based ESR values to the samples (Table 8), thebold calibration line and the observed temperatures were used. Inearlier measurements of effective absorptance a, values on the order of0.2 were measured. Then, an accuracy of 0.01-0.02 was achieved, about 5to 10% of the value. In the current measurements with larger values ofa, errors as large as about 0.04 may be present.

The data in FIG. 18 cluster into three groups. The lowest temperaturegroup is associated with the ruby pigmented coatings over a whiteprimer. The three samples near 23° C. temperature rise were rubypigmented over a yellow primer, and the warmest group contained thecoatings with copper silicate pigments (Egyptian blue, Han blue, and Hanpurple) over a yellow primer. Within the lowest temperature group, thereis a correlation of temperature with fluorescence intensity. Forexample, the two lowest data points at 16.5° C. and 16.6° C. bothexhibited bright fluorescence (Table 8).

TABLE 8 Solar reflectance (SR) and Effective Solar Reflectance (ESR)data for NIR fluorescent pigments PVDF-based coatings (Reflectance at550 nm, measured with filter to exclude fluorescence) SR from Temp. risespectrometer ESR in the sun, Film (corrected to from relativeFluorescence Visual P:B Thickness omit ruby temp. to air temp.brightness, bright- Pigment ratio (mils) fluorescence) meas. (K) peakheight ness ruby 0.2 0.94 0.682 0.648 18.8 11 0.703 ruby 0.2 2.71 0.6790.672 17.8 22 0.658 ruby 0.2 3.05 0.67 0.665 18.1 27 0.624 ruby 0.4 0.870.686 0.672 17.8 20 0.664 ruby 0.4 2.65 0.691 0.702 16.6 37 0.603 ruby0.4 3.03 0.679 0.665 18.1 36 0.583 ruby 0.8 0.78 0.691 0.658 18.4 270.636 ruby 0.8 1.76 0.703 0.685 17.3 41 0.573 ruby 0.8 2.49 0.688 0.70416.5 39 0.542 Egyptian 0.4 0.73 0.396 0.375 29.9 0.22 0.353 blueEgyptian 0.8 0.81 0.402 0.412 28.4 0.22 0.363 blue Han blue 0.4 0.810.345 0.35 30.9 0.12 0.212 Han blue 0.8 0.89 0.281 0.266 34.3 0.12 0.116Han 0.4 N/A 0.393 0.365 30.3 0.11 0.201 purple Han 0.8 0.89 0.351 0.34831 0.11 0.124 purple

Table 9 shows the temperature rise measurements using calibrated graysamples.

TABLE 9 Temperature rise measurements using calibrated gray samplesSpectrometer Temperature rise in absorptance (1-SR) the sun (K) 0.26715.5 +− 0.5 0.311 16.6 +− 0.3 0.506 26.0 +− 0.6 0.622 29.2 +− 0.6

Similar to the P:B ladder and film thickness study conducted with theruby pigment, a P:B ladder and film thickness study was conducted withan alkali earth copper silicate pigment (Sr (La,Li)CuSi₄O₁₀). Thispigment was incorporated into a PVDF-based coating system at P:B ratiosof 0.2, 0.4 and 0.8 and these coatings were applied over aluminumsubstrates coated with a yellow chrome primer and white primer. Threefilm thicknesses were applied for each P:B coating, namely 0.8 mils, 1.6mils and 2.4 mils. FIG. 19 shows the NIR fluorescence intensityincreased with increasing P:B ratio (i.e. increased pigment loading). Inaddition, NIR fluorescence intensity increased with increasing filmthickness for the 0.2 and 0.4 P:B coatings. For the 0.8 P:B coating, the1.6 mil thick film demonstrated more intense fluorescence than the 2.7mil thick film.

FIG. 20 shows the peak heights of the fluorescence of the coatings ofFIG. 19 as a function of the product of P:B ratio and coating thickness,that is, of pigment amount. As the pigment amount is increased, the peakheight smoothly increases from zero and bends over as additionalincrements of pigment contribute less to the fluorescence.

Example 9 Co-Pigments Using Two NIR Fluorescent Pigments

Coating formulations were prepared using two scaled-up NIR fluorescentpigments. Two NIR fluorescent pigments (ruby and Han Blue) wereformulated into two PVDF-based coatings. The first coating was darkbrown as ruby was incorporated into this formula at weight percentagesranging from 14% to 43% (FIG. 21 A). The second coating was black as HanBlue was formulated into this coating from 51% to 86% by weight (FIG. 21B). ESR measurements were conducted on these coatings. Measurements weremade on a control brown PVDF-based coating reference sample, and on asample which contained 43% ruby pigment. Spectrometer measurementsindicated that the solar reflectance values were 0.264 and 0.331,respectively. Fluorescence measurements on the ruby sample did showcharacteristic ruby fluorescence, but the amount was one or two ordersof magnitude lower than ruby without other pigments. The ESRmeasurements yielded 0.256 and 0.325, both values deviating from thespectrometer measurements by less than 0.010.

SrCuSi₄O₁₀ (large particles) was mixed with yellow (an organic yellowpigment, Liquitex “azo” yellow-orange (Diarylide yellow, PY83 HR70), anda mixed metal oxide, Shepherd 193) to make NIR fluorescent greencoatings. FIG. 22 shows coatings including Sr(La,Li)CuSi₄O₁₀ (Top),Sr(La,Li)CuSi₄O₁₀ with azo yellow (Bottom left) and Sr(La,Li)CuSi₄O₁₀with with Shepherd yellow 193 (Bottom right). In both cases fluorescencewas similar to that of the blue alone (Table 10). FIG. 23 shows aphotograph of the blue-shade black sample made with a SrCuSi₄O₁₀ (large)pigmented acrylic coating over orange over a bright white substrate. Theorange was a Liquitex cadmium light red hue (imitation) with one brushedcoating, which had an ESR of 0.451. The spectrometer reflectance was0.14 in the blue at 450 nm, 0.07 in the center of the visible (green) at550 nm and 0.10 in the red at 650 nm. Thus this sample was nearly black.

TABLE 10 Solar reflectance and effective solar reflectance data for‘green’ coatings prepared using different yellow pigments along withBlue 4 - Lot 2 Blue Solar Solar Benefit pigment Pigments in reflectancereflectance from Reflectance amount coatings (AM1GH) (ESR) fluorescence(550 nm) Substrate (g/m²)⁸ #193 yellow⁶ (buff) + 0.382 0.486 0.104 0.24Bright 90 Sr(La, Li)CuSi₄O₁₀ white Azo yellow⁷ + 0.338 0.479 0.141 0.26Bright 130 Sr(La, Li)CuSi₄O₁₀ white Sr(La, Li)CuSi₄O₁₀ 0.405 0.498 0.0930.173 Bright 100 white ⁶Available from The Shepard Color Company(Cincinnati, OH). ⁷Diarylide yellow, PY83 HR70. ⁸Amount of pigment perunit area.

Example 10 Co-Pigments Using NIR Fluorescent Pigments and IR ReflectivePigments

A control mocha PPG Duranar® coil coating was prepared by blending PPGDuranar® clear, IR reflective black, flatting slurry, red, white andyellow tint pastes to achieve the desired color.

An experimental mocha PPG Duranar® coil coating was prepared using NIRfluorescent pigments and IR reflective pigments. A blue tint pastecomprising NIR fluorescent Han blue and an orange tint paste comprisingIR reflective Orange 10C341 were prepared in a Duranar® formula. Theblue and orange tint pastes were mixed to attain the same color as thecontrol mocha coating. The experimental mocha coating and control mochacoating are shown side-by-side in FIG. 24 .

The substrates used for this evaluation were chrome primed aluminumsubstrates, which were coated with a white PPG Duranar® coating. Theexperimental and control mocha Duranar® coatings were coated onto thesubstrates and cured at 480° F. for 30 seconds to reach a final filmthicknesses of 74 micrometers.

NIR fluorescence measurements conducted on coated substrates shown inFIG. 24 indicated that the experimental mocha coating containing NIRfluorescent Han blue and IR reflective orange displayed NIR fluorescence(when excited at 600 nm), while the control mocha coating containingonly IR reflective pigments did not exhibit any fluorescence (whenexcited at 600 nm) (FIG. 25 ).

The dashed curve of FIG. 25 is for the experimental mocha coatingcontaining NIR fluorescent pigment and IR reflective pigment. The solidcurve of FIG. 25 is for the control mocha coating containing IRreflective pigment. The excitation wavelength was 600 nm. The emissionmeasurement range was from 650 nm to 1700 nm. NIR fluorescencemeasurements were conducted with a PTI QM-500 QuantaMaster™ NIRspectrofluorometer equipped with an InGaAs detector.

To determine the cooling benefit of the experimental mocha coating, boththe control mocha coating and the experimental mocha coating were placedunder heat lamps for the same amount of time. The surfaces of the coatedsubstrates were monitored over a 10-minute period. The experimentalmocha coating, which contained both NIR fluorescent Han blue and IRreflective orange was consistently 10 degrees cooler than the coatingfrom the control mocha coating, which contained IR reflective black.Upon reaching equilibrium, the temperature of the coating surface of theexperimental mocha coating was 160° F., while the temperature of thecontrol mocha coating surface was 170° F.

Example 11 Accelerated Testing, Outdoor Exposure and ThermalMeasurements

In addition to conducting weathering studies, thermal measurements wereconducted by using a portable field testing station to evaluate theperformance of coatings containing NIR fluorescent pigments. Theportable field testing station is equipped with a pyranometer,anemometer, wind vane, and thermocouples (samples are on R4 foaminsulation). The DataTaker™ 500 is capable of measuring up to eightsamples (3″×3″) along with an ambient sensor.

Thermal measurements, were conducted on a series of coated substratesusing the field station. The brown coatings evaluated contained varyinglevels of ruby pigment (14-43% by weight) and a brown co-pigment. WhileESR measurements were not conducted, temperature measurements of thepanels were made (FIG. 26 ). The coatings with ruby pigment levels morethan 30% by weight were about 4-5° C. cooler than coatings containingless than 30% ruby pigment.

Example 12 Thermal Test of the Cool IR Fluorescent Pigment Concept inSunlight

Substrates used are 3″×3″ aluminum sheets.

TABLE 11 Measurements with the SS Reflectometer (manufactured by Devices& Service Corp.) Ruby layer Off- 3 Ruby layer over white Bare ruby SSRAl white coats on 3 coats overcoated layer on channel substratereference white white with clear Spectralon spectralon 6.173 .626 .646.876 .527 .485 1.5E .644 .653 .897 .598 .552 L1 .740 .572 .846 .702 .621.964 .807 L2 .606 .684 .953 .773 .722 .980 .793 L3 .550 .730 .940 .117.124 .974 .120 L4 .497 .235 .238 .054 .064 .954 .061

The off-white reference film is made by mixing about 1 part in 20 ivoryblack into white. The ruby layer over white is not as reflective as the(3 coats of) white, even in the infrared (L1) channel. The roughness ofthe ruby layer may be contributing to a measurement artifact. It isknown that the SSR will read low if it is raised a bit from the surface.The same reduction in reflectance happens with a ruby layer onspectralon. Total internal reflection inside the ruby crystals may alsocontribute to reduced infrared reflectance.

The clear overcoat is used because it was thought it would reducescattering. However the reflectance in the L3 and L4 channel is notreduced as desired. Thus, the clear coat may be a liability; however itdoes keep the rubies attached to the substrate. A clear coat may stillbe helpful if small ruby particles are used as IR fluorescent pigment.

From the highlighted measurement the overall solar reflectance(excluding fluorescence) is roughly 0.485. This figure will be too highdue to fluorescence in the red due to blue and green light. The lamphowever is not an efficient emitter of blue and green light, so theerror may not be large. Also, the instrument may read low due to sampleroughness in the L1 and L2 channels. Overall, based on what is knownabout the non-fluorescent part of the solar reflectance is that it isroughly 0.5. This figure is in contrast with the overall effective solarreflectance as will be determined by the thermal measurement, which isabout 0.706.

Thermal Determination of Effective Reflectance R_(eff) in Sunlight,about 0.706.

The sample under test is the 3 inch square aluminum substrate with 3coats of white paint, a layer of rubies [each with a square outline butotherwise cut as a gem, 5 mm on a side, with pyramidal shape about 3 mmhigh, #5 stones (expresses how dark red they are)] (commerciallyavailable from PehnecGems; Garden Grove, Calif.), and a visiblytransparent top coat [Golden Soft Gel (Gloss)]. About ⅙ of the sample isnot covered with rubies; this portion of the sample has a solarreflectance of 0.876. The off-white reference coating, also on a 3 inchsquare Al substrate, has a solar reflectance of 0.646.

A chaise lounge with fabric covered cushion is used as a support for thesamples. The back is tilted so the samples faced directly into themid-day sun. A light beige towel is placed under the samples. IRtemperature measurements the day before the measurements reported hereshow that the towel temperature is 50 to 52° C. while the reference tempis 48 to 50° C. Previous measurements show that sample temperatures canbe perturbed by the temperature of the surrounding surface, so an effortis made to use a light-colored surface.

Measurements are made near solar noon. A slight breeze is present.During the measurements the air temperature changes from 37 to 38° C.,average value 37.5° C. The temperature rise of the off-white referenceis 21.34° C. above air temp., as measured with a data logger by athermistor underneath the sample. The test coupon is only 14.81° C.above air temp. Therefore, the test sample has a solar reflectance inexcess of 0.646. Temperature measurements of the sample tops with an IR“gun” range from 1 to 3 degrees higher and would yield similar resultsto the forthcoming results, had they been used.

The radiative cooling effect is estimated at 0.9×70 W m⁻² (mid-latitudesummer value). Solving for the effective solar absorption, one obtains0.265. Also, the sum of the radiative and convection heat transfercoefficients is 13.6 W m⁻²K⁻¹ (a small value, which indicates low windspeed). Finally, correcting for the fact that ⅙ of the sample has a lowabsorption, one find a_(eff)=0.294 for the ruby-coated part of thesample. Thus the effective solar reflectance is R_(eff)=0.706.

While it is uncertain as to the non-fluorescent part of the solarreflectance it seems likely to be near 0.5. The measured value of 0.7for the overall effective reflectance is quite improbable without asignificant contribution from fluorescence. Only the visible portion ofsunlight contributes to the fluorescence here, as the UV is absorbed bythe clear overcoat. The visible portion is about 0.45 of the total. Thefraction of loss due to the Stokes shift is about (550/700), the ratioof the center wavelength to emission wavelength. Further, the quantumefficiency of the fluorescence is believed to be about 0.7. The productof these three numbers is 0.25, so that the fluorescence mightcontribute as much as this to the effective solar reflectance.

Overall, the picture is consistent, and it is concluded that the use ofruby as a red IR fluorescent pigment can lead to anomalously high solarreflectance, due to fluorescence near 700 nm (694 nm). There is also acomplex addition emission spectrum extending from 700 to 800 nm. Thehuman eye is not very sensitive at 700 nm, so for some applications thefluorescence is invisible. Prior architectural materials withreflectance as large as 0.7 are all white, off-white or bright yellow.

Example 13 Thermal Test of the Cool IR Fluorescent Pigment Concept inSunlight

A crude coating is made using the proposed process that resulted in apink IR fluorescent pigment (1% Cr₂O₃ by weight in Al₂O₃, too light tobe called red). The powder synthesis uses a combustion synthesis methodvery similar to that reported by Kingsley (1988) (recipe doubled, 10%extra urea used). While the coating is too viscous for standardapplication techniques, it is successfully applied to a substrate usingrudimentary spreading with a spatula. Using 3.4 g of IR fluorescentpigment and 5.4 g of Liquitex Gloss Medium & Varnish for a 8 cm×8 cmsquare, the visible reflectance at 550 nm is 0.42, which corresponds toan L* of 65. The effective solar reflectance is 0.81.

FIG. 28 shows results from preliminary tests of the sample describedabove, three samples are identified by their solar absorptance, a asmeasured with a spectrometer, whereas the pink data points represent thesample under test. Temperature fluctuations are caused by gusts of wind,but each sample tracks the others. Interpolation indicates that the IRfluorescent pigment has an effective solar absorptance of 0.19,equivalent to an effective solar reflectance of 0.81.

Further results are shown in FIG. 29 . The weight percent of Cr₂O₃dopant in the Al₂O₃ host lattice is 0%, 0.2%, 1%, 2%, 3%, and 4%.

The present invention further includes the subject matter of thefollowing clauses.

Clause 1: A coating composition comprising: (i) a film-forming resin;(ii) an infrared reflective pigment; and (iii) an infrared fluorescentpigment different from the infrared reflective pigment.

Clause 2: The coating composition of clause 1, wherein, when the coatingcomposition is cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, the coating has a greatereffective solar reflectance (ESR) compared to the same coating exposedto the radiation comprising fluorescence-exciting radiation exceptwithout the infrared fluorescent pigment.

Clause 3: The coating composition of clause 1 or 2, wherein, when thecoating composition is cured to form a coating and exposed to theradiation comprising fluorescence-exciting radiation, the coating has anESR of at least 0.25.

Clause 4: The coating composition of any of clauses 1 to 3, wherein,when the coating composition is cured to form a coating and exposed tothe radiation comprising fluorescence-exciting radiation, a temperatureof the coating at a time (t1) after being exposed to the radiationcomprising fluorescence-exciting radiation is lower compared to the samecoating exposed to the radiation comprising fluorescence-excitingradiation except without the infrared fluorescent pigment at the time(t1) after being exposed to the radiation comprisingfluorescence-exciting radiation.

Clause 5: The coating composition of any of clauses 1 to 4, furthercomprising a colorant.

Clause 6: The coating composition of any of clauses 1 to 5, wherein theradiation comprising fluorescence-exciting radiation is produced fromsunlight, incandescent light, fluorescent light, xenon light, laser, LEDlight, or a combination thereof.

Clause 7: The coating composition of any of clauses 1 to 6, wherein theinfrared reflective pigment reflects at a first wavelength and theinfrared fluorescent pigment fluoresces at a second wavelength, andwherein a balance of the coating composition is transparent at the firstwavelength and second wavelength.

Clause 8: The coating composition of any of clauses 1 to 7, wherein theinfrared fluorescent pigment comprises Han purple, Han blue, Egyptianblue, ruby, a cadmium-containing pigment, azurite, ploss blue, smalt, ora combination thereof.

Clause 9: The coating composition of any of clauses 1 to 8, wherein theinfrared fluorescent pigment absorbs visible radiation.

Clause 10: The coating composition of any of clauses 1 to 9, wherein theinfrared the fluorescent pigment absorbs visible radiation such that thecoating composition exhibits a dark color.

Clause 11: A multi-layer coating comprising: (i) a first coating layercomprising a cured infrared reflective coating composition; and (ii) asecond coating layer overlaying at least a portion of the first coatinglayer, the second coating layer comprising a cured coating compositionaccording to any of clauses 1 to 10.

Clause 12: A substrate at least partially coated with the material ofany of clauses 1 to 10.

Clause 13: The substrate of clause 12, wherein the substrate comprisesat least a portion of a building substrate.

Clause 14: The substrate of clause 13, wherein the building substratecomprises at least a portion of an exterior panel, roofing material, orindustrial substrate.

Clause 15: The substrate of any of clauses 12 to 14, wherein thesubstrate comprises a metallic or non-metallic portion.

Clause 16: A method of reducing the temperature of an articlecomprising: (a) applying a coating composition to at least a portion ofa surface of an article, the coating composition comprising (i) afilm-forming resin, (ii) an infrared reflective pigment, and (iii) aninfrared fluorescent pigment different from the infrared reflectivepigment; and (b) curing the coating composition to form a coating on thearticle, wherein, when the coating composition is cured to form acoating and exposed to radiation comprising fluorescence-excitingradiation, the coating has a greater effective solar reflectance (ESR)compared to the same coating exposed to the radiation comprisingfluorescence-exciting radiation except without the infrared fluorescentpigment.

Clause 17: The method of clause 16, wherein, when the coatingcomposition is cured to form a coating and exposed to the radiationcomprising fluorescence-exciting radiation, the coating has an ESR of atleast 0.25.

Clause 18: The method of clause 16 or 17, wherein, when the coatingcomposition is cured to form a coating and exposed to the radiationcomprising fluorescence-exciting radiation, a temperature of the coatingat a time (t1) after being exposed to the radiation comprisingfluorescence-exciting radiation is lower compared to the same coatingexposed to the radiation comprising fluorescence-exciting radiationexcept without the infrared fluorescent pigment at the time (t1) afterbeing exposed to the radiation comprising fluorescence-excitingradiation.

Clause 19: The method of any of clauses 16 to 18, wherein the radiationcomprising fluorescence-exciting radiation is produced from sunlight,incandescent light, fluorescent light, xenon light, laser, LED light, ora combination thereof.

Clause 20: The method of any of clauses 16 to 19, wherein the articlecomprises at least a portion of a building substrate.

Clause 21: The method of clause 20, wherein the building substratecomprises at least a portion of an exterior panel, roofing material, orindustrial substrate.

Clause 22: The coating composition of any of clauses 1 to 10, whereinthe infrared fluorescent pigment comprises SrCuSi₄O₁₀, Sr(La,Li)CuSi₄O₁₀, Ba(La, Li)CuSi₄O₁₀, or a combination thereof.

Clause 23: The coating composition of any of clauses 1 to 10, furthercomprising an infrared transparent pigment.

Clause 24: The coating composition of any of clauses 1 to 10, whereinthe infrared fluorescent pigment fluoresces in the near-infrared regionof the electromagnetic spectrum when excited by the radiation comprisingfluorescence-exciting radiation.

Clause 25: A coating composition, comprising: a film-forming resin; aninfrared reflective pigment; and an infrared fluorescent pigmentdifferent from the infrared reflective pigment, wherein the infraredfluorescent pigment comprises at least one of Egyptian blue(CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀,ruby, azurite (Cu₃(CO₃)₂(OH)₂), ploss blue, smalt, or some combinationthereof, wherein the infrared fluorescent pigment has an averageparticle size of from 100 nm to 10 microns, wherein the coatingcomposition is substantially free of infrared fluorescent pigmentshaving an average particle size of more than 10 microns, wherein theinfrared reflective pigment reflects at a first infrared wavelength andthe infrared fluorescent pigment emits radiation at a second infraredwavelength, and wherein a balance of the coating composition istransparent at the first infrared wavelength and second infraredwavelength.

Clause 26: A substrate at least partially coated with the coatingcomposition of clause 25.

Clause 27: The substrate of clause 26, wherein the substrate comprisesat least a portion of a transportation vehicle.

Clause 28: The substrate of clause 27, wherein the transportationvehicle comprises an aircraft.

Clause 29: The substrate of clause 26, wherein the substrate comprises afiber reinforced polymer composite.

Clause 30: A transportation vehicle at least partially coated with thecoating composition of clause 25.

Clause 31: An aircraft at least partially coated with the coatingcomposition of clause 25.

Clause 32: The aircraft of clause 31, wherein, when the coatingcomposition is cured to form a coating and exposed to radiationcomprising fluorescence-exciting radiation, the coating has an effectivesolar reflectance (ESR) of at least 0.25.

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention. While thepresent invention has been described with reference to the specificembodiments thereof, it should be understood by those skilled in the artthat various changes may be made and equivalents may be substitutedwithout departing from the true spirit and scope of the invention. Inaddition, many modifications may be made to adapt a particularsituation, material, composition of matter, process, process step orsteps, to the objective, spirit and scope of the present invention. Allsuch modifications are intended to be within the scope of the claimsappended hereto.

The invention claimed is:
 1. A multi-layer coating, comprising: a firstcoating layer comprising a cured infrared reflective coatingcomposition; and a second coating layer overlaying at least a portion ofthe first coating layer, the second coating layer comprising a curedcoating composition wherein the coating composition comprises: afilm-forming resin; an infrared reflective pigment; and an infraredfluorescent pigment different from the infrared reflective pigment,wherein the infrared fluorescent pigment comprises at least one ofEgyptian blue (CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple(BaCuSi₂O₆), SrCuSi₄O₁₀, ruby, azurite (Cu₃(CO₃)₂(OH)₂), ploss blue,smalt, or some combination thereof, wherein the infrared fluorescentpigment has an average particle size of from 100 nm to 10 microns,wherein the coating composition is substantially free of infraredfluorescent pigments having an average particle size of more than 10microns.
 2. The multi-layer coating of claim 1, wherein the infraredfluorescent pigment absorbs visible radiation.
 3. The multi-layercoating of claim 2, wherein the infrared fluorescent pigment absorbsvisible radiation such that the coating composition exhibits a darkcolor.
 4. The multi-layer coating of claim 1, wherein the coatingcomposition further comprises an infrared transparent pigment.
 5. Themulti-layer coating of claim 1, wherein the multi-layer coating exhibitsan effective solar reflectance (ESR) of at least 0.25 when exposed toradiation comprising fluorescence-exciting radiation.
 6. The multi-layercoating of claim 1, wherein, when the multi-layer coating is exposed toradiation comprising fluorescence-exciting radiation, a temperature ofthe multi-layer coating at a time (t₁) after being exposed to theradiation is lower compared to the same multi-layer coating exposed tothe radiation except without the infrared fluorescent pigment at thetime (t₁) after being exposed to the radiation.
 7. The multi-layercoating of claim 1, wherein the second coating layer comprises aneffective amount of the infrared reflective pigment, such that thesecond coating layer has a solar reflectance, measured according to ASTME903-96 in the wavelength range of 700-2500 nm, that is at least 2percentage points higher the same second coating layer except that theinfrared reflective pigment is not present.
 8. The multi-layer coatingof claim 1, wherein the infrared fluorescent pigment absorbs radiationat a first, shorter wavelength and emits radiation at a second, longerwavelength, wherein the second, longer wavelength is in the infraredregion.
 9. The multi-layer coating of claim 1, wherein the infraredreflective pigment does not substantially absorb the second infraredwavelength.
 10. A substrate at least partially coated with a coatingcomposition, the coating composition comprising: a film-forming resin;an infrared reflective pigment; and an infrared fluorescent pigmentdifferent from the infrared reflective pigment, wherein the infraredfluorescent pigment comprises at least one of Egyptian blue(CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple (BaCuSi₂O₆), SrCuSi₄O₁₀,ruby, azurite (Cu₃(CO₃)₂(OH)₂), ploss blue, smalt, or some combinationthereof, wherein the infrared fluorescent pigment has an averageparticle size of from 100 nm to 10 microns, wherein the coatingcomposition is substantially free of infrared fluorescent pigmentshaving an average particle size of more than 10 microns, wherein theinfrared reflective pigment reflects at a first infrared wavelength andthe infrared fluorescent pigment emits radiation at a second infraredwavelength, and wherein a balance of the coating composition istransparent at the first infrared wavelength and second infraredwavelength; and wherein the substrate comprises a fiber reinforcedpolymer composite.
 11. A transportation vehicle at least partiallycoated with a coating composition, the coating composition comprising: afilm-forming resin; an infrared reflective pigment; and an infraredfluorescent pigment different from the infrared reflective pigment,wherein the infrared fluorescent pigment comprises at least one ofEgyptian blue (CaCuSi₄O₁₀), Han blue (BaCuSi₄O₁₀), Han purple(BaCuSi₂O₆), SrCuSi₄O₁₀, ruby, azurite (Cu₃(CO₃)₂(OH)₂), ploss blue,smalt, or some combination thereof, wherein the infrared fluorescentpigment has an average particle size of from 100 nm to 10 microns,wherein the coating composition is substantially free of infraredfluorescent pigments having an average particle size of more than 10microns, wherein the infrared reflective pigment reflects at a firstinfrared wavelength and the infrared fluorescent pigment emits radiationat a second infrared wavelength, and wherein a balance of the coatingcomposition is transparent at the first infrared wavelength and secondinfrared wavelength.
 12. The transportation vehicle of claim 11, whereinthe transportation vehicle comprises an aircraft.
 13. The transportationvehicle of claim 12, wherein, when the coating composition is cured toform a coating and exposed to radiation comprising fluorescence-excitingradiation, the coating has an effective solar reflectance (ESR) of atleast 0.25.
 14. A substrate at least partially coated with themulti-layer coating of claim
 1. 15. The substrate of claim 14, whereinthe substrate comprises a fiber reinforced polymer composite.
 16. Atransportation vehicle at least partially coated with the multi-layercoating of claim
 1. 17. An aircraft at least partially coated with themulti-layer coating of claim
 1. 18. The aircraft of claim 17, wherein,when the coating composition is cured to form a coating and exposed toradiation comprising fluorescence-exciting radiation, the coating has aneffective solar reflectance (ESR) of at least 0.25.